My wish-list for "beyond N900":
5" WXGA (1280x800) Bezel-less, 24 bit Color Display
....~4.36" x ~2.45"; basically the same size as N900
....Can show 720p (1280x720) content natively
Haptic multi-touchscreen
4 row full QWERTY keyboard (5 row a plus)
Better CPU(s)/GPU(s)
Huge RAM & Storage
3G, 4G, etc. Must be usable in California!!!
1 easily hot-swappable uSD slot (2nd "internal" a bonus)
Easily swappable Battery ("Hot Swappable" a bonus)
A-GPS
6 D.F. Accellerometers/Gyros
Compass
Camera (Larger aperture and detector + more MPix)
ATSC tuner (or mobile equiv.)
AM/FM radio
.... include an antenna solution for when using bluetooth headsets
Lays flat to type
HDMI Out