Id say if we were keeping this more in the realm of possible stock software enhancements that there are a few jailbreak functions I could see coming in an x.0 software release.
- A way to quick reply to messages, be it from sms or pop notifications. Loading an app to type a one word message wasn't working for me (thanks biteSMS).
- SBSettings type toggle to change commonly accessed settings from anywhere. Again, stupid design to plunk all these items in a settings app with no possible way to toggle them outside that app.
- Lockscreen info. I honestly don't use intelliscreen or lockinfo but I can definitely see the appeal of them. Having biteSMS work from the lock screen is good enough for me.
I see those as possible, some of the more invasive JB software will never see the light of day on the non JB side of things.
I doubt we'll ever see themes. I do think more customizable options will come, maybe on how the notifications system works (ie, not while running certain apps or during certain times). I'd also like to see some enhancements to some of the stock apps like contact pictures in sms and a character counter akin to biteSMS implementation. It would also be nice if some of their other stock apps got a facelift / overhaul or at least allow us to hide the stupid things. Most of the functionality of the "widget" apps like weather and stocks can be duplicated and vastly improved upon using 3rd party software. As they are now they seem quite pathetic compared to what is in the app store.