That's a good question.
We all know Apple, and their methods on surprises!
What I've been thinking is that when Apple introduced the world with the 4S I was really disappointed.
We've been waiting for the new iphone and then >###$#$# ..
However, I have a thought that apple will introduce a totally new iPhone this year or at the beginning on the next year, and the iPhone 4S & iPad 2, it was just matter of buying some time to finish what they're preparing for the new iPhone.
If that is right, then the screen size & LTE are not the only two will be in the new iPhone.
Remember that Apple has improved their Apple Store, and still improving.
So The new iDevices will be totally worth patience.
And Since there're many computations around the market, I think Apple will go more further for their new iDevices.. and they might use the nano technology, which will make the iPhone more Powerful, Thinner, and Faster.
It'll have a HD screen(up to 450ppi) with a new size between 4" to 5", and that means they might replace the home button to a screen touch button(or marge it with the power button).
and the edges of the iphone will be like the 3gs (rounded).
(I know I have a big imagination

)