Marco Arment does a good job speculating what Apple could release in the coming fall:
I do not believe that they’ll change the screen size to conserve cost or physical size. A screen-size change would incur too large of a cost in software and the app ecosystem.
Hopefully he’s right, as I don’t like to carry a 4″+ phone in my pocket. It’s just too big.
He also says that there won’t be a new iPad. Apple said that 2011 would be the year of the iPad 2, so it wouldn’t make much sense releasing a new one, also because “Apple is still having trouble keeping up with demand for the iPad 2”.