To be honest, I would much rather see a thicker phone with a longer battery. My current iPhone (the 3g) feels unnecessarily thin to me.

What I would really like to see would be the option for a larger battery.

Yes, people don't really appreciate this. With Canon Powershot cameras, they went thicker when they added image-stabilization a few years ago, and that quarter inch or whatnot really made a huge difference in how big it felt and how pocketable it was.