Well there's only one worthy successor to the N900 (and the N950 doesn't count because you can't get it):

The SG NOTE.

-The fastest SoC (cpu, gpu and ram) available
-The highest resolution (1280x800) screen in any mobile device (not counting the Grid10)
-The "best screen" because of the battery drain, viewing angles, deep blacks and good colour reproduction, and ten-point multitouch
-The largest screen'd phone... at 5.3" photos, movies and games are pleasant and virtual typing is bearable.
-Did I say Apps and heaps of customizations?
-It has all the modern connectivities (NFC and LTE pending on future version)
-It has an N-Trig/active digitizer pen "S Pen"
-It's very light and fairly compact still fits into my pockets!
-Excellent call quality, earpiece, loudspeaker, radio signals, battery life etc etc

I think there will be a Ubuntu (chroot) port to it, and perhaps a proof-of-concept-MeeGo-port too