Might be a bit late in this conversation...my apologies, hehe; just wanted to share my opinion!
I love the 5 row Sidekick keyboard...haven't really seen any phones with it other than the Sidekick. I think the G1 has it, maybe?
I'd love to see;
• Lit trackball
• 5 MP+ camera, flash could not hurt
• Updated browser, for sure
• Threaded messaging would be nice, but have the option to turn it ON or OFF
• The messaging in Sidekicks are totally outdated, of course with it being on a different operating system, I imagine seeing everything revamped... including the messaging
• In-front camera
• Slimmer than any of the previous Sidekicks
That's all I can think of right now.
oh and I hope they wouldn't call a Sidekick a 'Sidekick' without it twisting/flipping out like all the others, (excluding the Slide)