Up until this year, Apple always released new iPhones in June or July, and certain details—enclosure and spec changes—tended to leak out ahead of time, providing an early idea of what to expect. This year was different. Apple is waiting a few extra months to debut new iPhone hardware, and there have been so many different leaks that no one’s sure quite what to make of them.

Since we’ve received many inquiries from readers as to what’s likely to happen, we wanted to share some educated speculation with you—essentially the scenarios that our editors have been discussing in anticipation of official announcements from Apple. Most of our attention focuses on new iPhone hardware; the other part is on what changes, if any, can be expected from data plans as iPhones begin to transition into the 4G/LTE era.

New iPhones

Though consumers only remember the products Apple actually releases, it’s well-established that the company has Plan A, Plan B, and possibly even Plan C scenarios mapped out for a given year. Multiple options enable production lines to keep rolling when, for example, the third-generation iPod touch’s rear camera has last-minute problems and needs to be left out.

Based on official and unofficial leaks, it appears that Apple has been working on at least three different iPhones for possible 2011 release. The first is a tweaked “iPhone 4S” that will largely resemble the iPhone 4—metal band in the center—and could either become a cheap or a same-priced sequel to the current iPhone 4, depending on how manufacturing proceeds with the iPhone 5. Second is the true iPhone 5, a redesigned thinner model that could be either a same-priced or more expensive follow-up to the iPhone 4, depending on manufacturing yields and marketing plans. Third is a smaller iPhone—let’s call it iPhone Mini*—which is designed to be a basic entry-level model, and possibly dependent on iTunes in the Cloud. We see three scenarios as being possible at this point.

(a) iPhone 3GS/Mini + iPhone 4S. Though the iPhone 3GS is arguably long in the tooth, Apple has repeatedly hinted that it’s interested in offering an affordable phone in developing markets—notably China. Under the most “conservative” scenario, Apple could keep the iPhone 3GS around as a super-cheap model and continue to offer it to GSM customers. Unfortunately, most of the Chinese market uses a separate cellular standard called TD-SCDMA that is not supported by any current iPhone. An iPhone with at least a little new engineering and a low price tag would be required to reach the Chinese masses. This budget model could be the iPhone Mini, adding worldphone support, including the TD-SCDMA support Apple needs to expand further in China. It would not aim for speed or performance improvements—it would be deliberately weaker than other iPhones. Note that there have been no known component or test result leaks for such a device. (* Our editors continue to debate whether Apple would call it the iPhone Air, iPhone Cloud or something else.)

In this scenario, Apple would upgrade the iPhone 4 with an A5 chip, better 8MP camera, more storage space, and possibly a slightly larger screen, and call it the iPhone 4S or something similar. We think of this as the “engineering problems” scenario, in which the more advanced iPhone 5 has proved too difficult to manufacture, and Apple makes a pragmatic decision to expand the iPhone footprint as best as it can.

(b) iPhone 4S + iPhone 5. Under this scenario, a different pair of iPhones debut at the same time. One is the iPhone 4S, which has been customized here as a budget-conscious replacement for the iPhone 3GS, offering similarly low storage space and very modest performance tweaks, quite possibly with worldphone support so that Apple can sell a single model in most parts of the world. Even TD-SCDMA support could have been added via quiet testing of an inconspicuously iPhone 4-like device in China. The other device is the iPhone 5, a thinner but taller and wider model with a larger screen (3.7”), worldphone support, an upgraded camera, and possibly 4G/LTE functionality. This iPhone has been completely redesigned from the iPhone 4, including a gesture-sensitive Home Button that can be used for app switching.

We think that this is the most likely scenario. Part leaks and comments from Apple appear to suggest the continued sale of an iPhone 4 in modified form this year, along with a streamlined but more powerful iPhone 5. The only big question mark is whether the iPhone 5 gets 4G/LTE support, and there are active debates right now as to whether a thinner iPhone would have enough space for all the hardware necessary to provide a good 4G experience. LTE remains sketchy enough across the world that Apple could pass on this feature until next year’s model, marketing concerns aside. This seems very possible, with LTE support coming first to the iPad family.

(c) iPhone 3GS/Mini + iPhone 4S + iPhone 5. Under this possible but challenging scenario, Apple uses 2011 to transform the iPhone into a true family of products. An entry-level, super-inexpensive model is offered for budget-conscious users, and is either the iPhone 3GS or the supposedly smaller, cloud-dependent iPhone Mini. Here, the iPhone 4S is offered as a speedier mid-range model, replacing the current iPhone 4. iPhone 5 debuts as the high-end model for users who are willing to pay more for a superior camera, bigger screen, and possibly more storage space.

Which of these scenarios will Apple go with? It’s still unclear. But if we were betting based on the official and unofficial leaks to date, we’d guess (b); (c) would be an aspirational goal. That said, it is interesting—surprising, even—that there have been no reports of slowed current-model iPhone production, no slippage in iPhone 3GS or iPhone 4 availability from Apple or third-party retailers, or other signs that past models are on the cusp of being phased out. Such signs normally precede a new iPhone launch, and may suggest that Apple will stagger new hardware rollouts globally to more gently ramp down production this year.

New Data Plans?

When Apple transitioned from the original iPhone to the iPhone 3G, there was a period of hand-wringing over increased monthly data charges—unlimited EDGE data plans went for $20, and unlimited 3G plans started at $30. If you’re wondering whether something similar is likely to happen with 4G/LTE phones, the answer appears to be “no,” at least in the United States and Canada. For the time being, AT&T, Verizon, and other companies seem to be okay with charging the same prices for 4G/LTE service as they did for bandwidth-capped 3G.

The big question is whether these companies will use the launch of new iPhones as an excuse to push existing “unlimited 3G” customers out of their grandfathered-in plans, and into limited 3G or 4G/LTE plans. AT&T has so far been using carrots rather than sticks to push customers to voluntarily make the transition, only allowing existing iPhone 4 users to add tethering/hotspot features if they move from unlimited plans down to limited ones. New users are required to choose limited plans. But now AT&T may try to force existing customers to give up their unlimited service for new hardware. We’re hoping that this doesn’t happen.

In any case, new iPhone hardware can be expected this fall—most likely at the end of September or beginning of October. What do you think will happen with the iPhone lineup this year? How should Apple evolve the family? We look forward to your comments below.