Both Best Buy and Radio Shack will offer the iPhone 4 on launch day, according to a new report and a series of Twitter updates, respectively. Citing a trusted unnamed source, Engadget reports that Best Buy will be offering the next-generation iPhone at launch, and that stores will apparently have no less than 45 units on hand—30 for the higher-capacity 32GB model and 15 of the 16GB units. Additionally, Radio Shack has confirmed via its Twitter account that it will be offering the iPhone 4 at launch, and will begin taking pre-orders with a $50 deposit on June 15, the same day as Apple. Interestingly, the company will also be accepting trade-ins for the iPhone 4, offering as much as $100 credit for iPhone 3G units and $200 for iPhone 3GS units; more information can be found on the company’s trade-in program website. Apple will launch the iPhone 4 in the U.S., France, Germany, the U.K., and Japan on June 24.