Let me get this straight - you really want an OS that doesn't yet exist, that might take a year or two to see it on a consumer product, that might come with some fugly UI (Maemo 5 UI is actually one of the best out there even if somewhat rough on the edges), and that, dispite all, once out will be probably available in one form or the other for the N900 (and even if it won't, the core is the same and applications will be easily portable), and that's what stopping you from getting the N900 which exists and works NOW?

I'm sorry, but that's a bit like saying that you don't want i7 because Windows 10 might not be able to run on it...