Based on the general theory applicable to desktops that "if it can run Windows, it can run GNU/Linux at least as well, if not better" ... if one of these new WPs have decent h/w specs then perhaps it would be worth trying to flash Meego/Cordia on to it? There are reports of various distros being stuck on existing WPs so perhaps ... just* a matter of isolating the hardware from the OS sufficiently to substitute.

As for a new phone now, if you want something that has the range of functionality of the N900? Err there's nothing out there mate!

*no small feat!