Engadget has strong evidence about the next iPhone. If true, then the next iPhone will have a matching glass back cover, replaceable battery, and SD card slot.
Even if you do not care about the iPhone, these features may wind up in future versions of the iPad. I am not interested in the glass back plate, but the SD card slot may have potential. USB would be nicer instead. The removable batteries would be a question mark. Considering the price of cell phone batteries, it could be not worth the cost to replace the batteries.