Apple boasts all the time how many apps they have and it would be a HUGE advantage to release the tablet with all these apps. If Apple keeps the tablet resolution the same ratio of the iPhone, say 4 times larger (1920X1280), they could easily resize all the images with little degradation and, with a little clever software, make all the current apps work. I am not saying the tablet will use the exact same SDK, but it could be a superset of the iPhone OS SDK. Application developers could optionally repackage their apps to take advantage of the new tablet features (whatever they are) and include correctly sized images.
I predict they will make the devices app compatible with at least the current line of iPhones/iPod Touches. At some point the two devices may branch apart so newer iPhone OS apps would not necessarily work on the tablet but they would still share enough to make developing for both fairly easy. So contrary to what most say, I am predicting the tablet to be a giant iPhone OS based device. It'll have a higher resolution screen, a redesigned home screen and additional UI features, but all current iPhone OS UI features will be supported. It's value would be:
- Full 1080p HD video (notice the above resolution),
- A great user experience for newspapers/magazines with subscriptions available through the iTunes store
- Native e-book reader using an Apple format available through the iTunes store
- An even better mobile browsing experience
- More convenient than a Macbook; always on (like iPhone) and smaller/lighter
- Faster processor, more RAM and larger hard drive than the iPhone/iPod Touch