I've held off buying the n810 because I didn't like a few things that changed from the N800 to the N810, particularly the lack of a second SDHC slot (getting stuck with an unremovable 2GB is unacceptable to me and seems like a step backwards from the N800 model).

Here's what I'd like to see in a newer model, realistically, and would effect my decision to immediately jump out and buy one.. I'll break it down into three categories: important things to retain from current models, new things I want to see and, lastly, things I don't want to see.

IMPORTANT THINGS TO RETAIN FROM CURRENT MODELS:
n800: TWO SDHC slots
n800: Speakers in the FRONT (On the sides/back on the n810? Weak.)
n800: Directional and other controls on the face
n8x0: Kickstand (one of the things that immediately impresses EVERYONE as useful)
n810: GPS built-in (wish I'd had that in my n800, very cool integration)
n810: Slide-out keyboard (more of a want, not a real NEED, I've found)
n810 WiMax Edition: The black metal style--MUCH nicer than anything else so far.

THINGS I WANT TO SEE:
Mouse support! PLEASE! There are many times where I'd LIKE a more accurate way to draw (with a drawing tablet) or hover over things (web browsing, tooltips, etc.) There would NOTHING quite like folding out my already-working Bluetooth keyboard and my almost-working Bluetooth mouse and my N800 tablet down.. and then effectively having the most portable faux laptop experience.
Open drivers to hardware (if Neuros can do this with frighteningly similar hardware--why can't a bigger, more established player like Nokia?)
Of course, faster processor and more memory.. my Palm Tungsten T5 is faster than either the N800 or the N810 and the T5 isn't even a Linux based Internet Tablet.

THINGS I DON'T WANT TO SEE:
Cell phone radio (I would prefer to have an external Bluetooth phone or USB modem device to do wireless networking so that I'm not tethered to a particular service)