Your question has no answer.

it HAS support, and its already UNSUPPORTED:

- Official support, no way. Nokia (maybe) will release pr1.3, and no one expects nothing after that.
- Unofficial support: a lot of parts are open source, that can be upgraded without the help of nokia. and here we have a big community that loves the n900 a lot.

Another question is what we have, and what we dont. Mainly here is the Application Store
- Milestone have the Android Store.
- Here at maemo, we have a joke (ovi store).

And the closed source parts, like the phone, modest for mail, and several subsystems

hope this helps