I would love a modern version of the N900/N810. If I could get one with a recent ARM processor, good slide out keyboard, and running a more desktop-oriented Linux install (meaning more hacking/developer friendly than just Android), I'd be seriously tempted. Sadly, I assume the current component prices would mean it would be too expensive to be realistic.
I'd buy an N810 formfactor right now with modern guts.
Not ARM but checkout the PinePhone, its also pretty much sold at cost (same as most Pine products)
Funny I tried to buy one of those breakout blackberry keyboards but they were sold out everywhere
This with DisplayPort Alt-Mode so it can be docked for desktop use is pretty much my dream device.