I’m not so worried about increasing storage capacity. I wouldn’t use it for music that much, except for maybe outside of streaming services, and I don’t plan on carrying any kind of movie collection on it. 32GB is, for me, the most (works just fine on my iPhone 4S…still nowhere near filling it up).
Probably won’t see Gigabit Wi-Fi either. Where would you be able to hook into that? I also don’t see Thunderbolt as being an option…and, again, what would you do with it if you had it?
Probably better cameras, faster processor, quad-core, and perhaps a retina display.