I just saw another potential N900 replacement... the "W3":

The Magic W3: the mini-PC with phone capabilities that's not a smartphone

No word on pricing or availability yet, but it runs an Atom processor, 32GB storage, 4.8" screen, camera, wifi, bluetooth, 3g, hdmi... the works. Plus it makes phone calls!

It comes installed with Windows 7 on it. The only issue I see is that there is Windows software for making calls, but I don't know if a Linux equivalent exists.