Besides all the good things on the N900, some of the things i would welcome on a N950 would be:

Dual analog sticks/pads/nubs
Resistive multitouch.
A more open high resolution high FPS camera hadware
Faster and better graphics and audio acceleration hardware
Out of the box capacity to run Symbian binnaries without the need for multibooting.
Four rows QWERTY keyboard
Designed such that using the keyboard and other buttons for gaming doesn't need to be so awkward
Speakers at the very least as loud and good sounding as on the N73 positioned such holding the device doesn't cover the speakers killing most of the sound.
Cable ports that don't get in the way of holding the device with the cables plugged
Multicore CPU
Way more root, programs and fast RAM memory
Dual rumble motors, each way stronger than the one in the N900 at full throttle
3 axial magnetomer
IR transceiver compatible with IRda and remote controls, with the emiter strong enough to be used as a night vision torch
Full duplex FM radio transceiver (to allow it be used as a walkietalkie), capable of transmitting strong enough to use with radio receivers without needing to be too close to them. And receiver capable of getting a clean signal without the need of an external antenna most of the time.
Full duplex completly software programable radios (the more the merrier) covering many different bands including WiFi, analog TV , RC toys etc (any that somewhere in the word people are allowed to transmit and/or receive without aquiring a license)
Discreet buttons in the back reacheable with the remaining fingers so you won't need to use just thumbs and leave the other finges iddling while playing games
Bigger screen without increasing the overall size too much.
Battery life of at least a whole day with heavy use.
USB OTG out of the box
Pico projector, laser, RGB, at least 16bpp and at least SVGA resolution (1024x768)
Decent "webcam"
3d (or really 2.5d , i don't expect volumetric sensing) depth/proximity sensing over the screen, for "multitouch" touchless input (mouse cursor hover, waving, flicking etc gestures etc, and if possible even scanning of objects)
High speed main camera (for nice slowmo shots)
Time of flight 3d photo and video capable main camera (kinda like http://video.google.com/videoplay?do...94784112768834 )
Kinda pushing it a bit, but an electronic nose capable of being used to identify all sorts of smells, like rotten food, BO, explosives etc would be awesomen to have; even better if it's stereo and with a fast SPS (smells per second ) rate to more easilly identify the source.
Programable aperture for the main camera ( like http://www.youtube.com/watch?v=8ENfPYpkHp4 )
A microfone array to filter sounds by the position of source.
OS and underlying components (including fimware) as open as the law allows (or more if they can get away with it)
Some sort of (near)realtime 6dof motion tracking system (perhaps using the 3d video capabilities of the main camera to analyze point of view change in relation to the enviroment together with the accellerometer and magnetometer?)
GPS capable of at least centimeter resolution at a high framerate.
8-way 9 screens scrollable desktop (toroidal topology).
As compatible with desktop linuces(sp?) as possible.
Unobstrusive video-out (with a squidlike adapter cable for all sorts of plugs, HDMI, VGA, RCA, video component etc, software would control which standard to transmit on; cables dedicated to specific standards could be sold separatedly) . Even better if it also ce used for video-in, same deal with the standards.
Out of the box capability for being as a standard bluetooth (and USB) webcam.
Out of the box (near)realtime headtracking capability, perhaps by default used for eyecandy in the OS interface for paralaxing (rendering GUI elements in 3d, buttons really raised, textboxes sunk etc, shortcut icons floating above the background and so on, probably a good idea to keep things the user can click on at the screen plane so they don't move as much), image viewer could display images like as if the device was a window (kinda like that Johnny Lee demo with the panoramic photo of a stadium) etc.
Screen that actually takes advantage of ambient light, even under sunlight (with the backlight turned off it should look as close as possible to a piece of paper with the screen contents printed on, and not like an old Gameboy that just had the batteries pulled off)



These are just some of the things i would like, there are others besides these.