Bearing in mind Android runs on top of a "virtual machine" (similar on Java) and the n900 only has a 600mhz cpu.

It's a nice idea - I'm pretty sure someone is already trying it - dual-boot hack.

If Maemo 6 will not be "officially" available on the n900 then maybe concentrate on efforts to create a "community" version of maemo 6 that runs on the n900 instead.