Well they really need to make a plan for something like this i mean android have updates OTA so you don't' really have to change your device in a sense only reason would be is hardware limitation hence G1 and donut debate. Maemo should use the same methods people can't keep coughing up 700+ dollars every year.

Sounds like something Apple would do hence there 1 year iphone deal (upgrading it every may) only difference is its subsidized so unless they subsidize the n900 i think that will be kind of foul.