If we're talking things that might be possible to upgrade now and not for a future model.....

-Easier way for newb's like me to 'make root'
-More customization- Themes, desktop (widgets, toolbar functions, etc.), browser (plugins, optimization, buttons- tabs, etc.)
-Better email
-I wanted better IM, but now there's Skype. So how about tweaking Skype so Voip really works (w/Video calls)
-Better full screen keyboard
-Google apps, like maps (a la iPhone)
-Google docs compatability
-More Games (nGage?)
-Better SDHC compatability- lets go 8+ gigs
-Support more video codecs
-USB Charging
-More camera functionality