So yesterday, I promised on Twitter that there would be a tablet-related update today. Here are a couple of late-breaking, interesting details that we’ve had double-confirmed by sources.

(a) Double Dock Connectors. We’re hearing that the tablet is going to have one on the vertical bottom edge and one on the horizontal bottom edge, enabling this device for the first time to be both mounted and charged either in portrait or landscape mode. iPhone and iPod touch users have long had to deal with the unusual sight of a cable or hard-mounted connector sticking out of the side of their devices when it’s being used as a widescreen video or game player, and accessory companies have struggled for the past three years to figure out ways to accommodate Cover Flow and the like in their speakers and docks. Two Dock Connectors fixes this, and depending on how Apple handles multiple accessory connections, could have some other nice benefits, as well.

(b) Antennas. The various reports of the tablet’s iPhone-ish-ness continue with the antenna compartment, which like the original iPhone has a long rear stripe for wireless radio broadcasting. This is necessary due to the metal used in the rest of the shell, which would inhibit radio performance, and the size of the stripe—not an iPod touch-sized pill—suggests room for nice-sized antennas, and 802.11n compatibility.

Obviously, nothing’s 100% certain here, but these details come from highly reliable sources.

The other interesting topic of discussion around here: pricing. I need to make clear that none of what follows comes from external sources—it’s purely our internal discussion and speculation—but it’s seriously worth thinking about in the lead-up to next week’s announcement.

It’s an absolute certainty that the tablet (or, uh, iPad) is going to have Wi-Fi functionality, and every piece of information we’ve had for many months has suggested that cellular service will be offered optionally to enable it to access the Internet when you’re not near an 802.11 hotspot. This naturally raises three related questions: “subsidy,” “type of data service,” and “service fees.”

(1) Subsidy. If one carrier, or two carriers, were to get rights to offer the tablet with multi-year data service contracts, they would likely cut the up-front price of the tablet in exchange for ongoing monthly revenues. The typical subsidies these days are in the $350-$400 range for a 2-year contract, such that an unlocked iPhone 3GS would sell for $599 and an AT&T locked one would sell for $199. A similar slice would apply, presumptively, to a tablet.

(2) Type of Data Service. We’ve heard theories that Apple will, matching Amazon’s Kindle approach, offer free coast-to-coast data services for the tablet. But that doesn’t really make a lot of sense when you think about it. Kindle and similar devices barely touch their data networks by comparison with data-hungry iPhones, which gobble plenty of data from the web and other types of apps. Might Apple’s partners offer a limited level of free service—basically sub-10MB iTunes Store and App Store downloads, so you can grab books, music, and the like in the same sort of way that Kindles work—with data plans for those who want full web access? Or will there be no such free offering: buy cellular data or use Wi-Fi, that’s it? And will voice minutes be offered at all for this device?

(3) Service Fees. Obviously, the fees will vary depending on what the cell companies are actually offering, but it’s worth noting that AT&T, T-Mobile, and Verizon are all in generally the same ballpark right now in offering data service packages for netbooks—the easiest analog to the tablet in terms of data hungriness. T-Mobile offers 200MB of data for $30 per month, with AT&T charging $35 for the same 200MB, and Verizon $40 as a base price for 250MB. All three companies offer 5GB of data for $60 per month, with T-Mobile also offering a less expensive $40 unlimited plan for certain devices.

Is anyone going to actually be willing to cough up $30-$60 per month for cellular access on a tablet? Our guess is that this would be a hard sell, particularly for the earliest wave of Apple tablet adopters—people who already likely have iPhone service contracts that would suddenly go way, way up in price for the tablet. This reality might well compel prospective service providers to offer more aggressive service pricing, or better yet, a combined iPhone and tablet service pricing plan.

Strictly speaking, there’s no reason that tablet and iPhone users should have to pay anything above the cost of their existing iPhone service contracts if they buy an unsubsidized device: the iPhone is capable of tethering, and in every country with tethering support (say, Canada) can connect to a Mac or PC via cable or Bluetooth to provide data access. Making the same connections between an iPhone and a tablet would be a no brainer. Interestingly, you wouldn’t even need an “unlimited” data plan to be comfortable doing this: the iLounge editor who tethers the most—Jesse in Canada—has used a whopping total of 8GB of data in one year between his iPhone and tethered MacBook without trying to limit himself in any way. He pays for 6GB of data per month and actually uses less than 1GB per month with tethering on the road. Obviously, the numbers would vary from person to person, but most people would be well under his usage numbers, and harder core video and audio streamers might easily go above it.

Even though an iPhone-tethered data solution would work for millions of potential tablet buyers, we’d be shocked if AT&T wouldn’t salivate over another opportunity to charge customers a $36 activation fee and additional monthly service fees, “necessary” of course because of the additional strains tablet access would place on its fragile infrastructure. That way, it could finally have enough cash on hand to make its network reliable. Right? Right?

Feel free as always to discuss and debate the possibilities in the comments section below.