Too many people here do not think before posting.

I'll consider the worst scenario (for pessimists and FUDders):

Nokia drops immediately support for the N900 and MeeGo isn't available for the N900. Apps between maemo & meego are not compatible. This is the worst scenario possible. What does it mean? N900 will be alive as always. Community added features like MMS (fMMS) , USSD (widget) and many other features. So why are you whining? If maemo isn't upgraded then you have the right to bug the hell out of bugs.maemo.org and get fixes. There are also alternatives to maemo. Meego will be ported unofficially for sure and if not other distros will. The things you should worry about is getting drivers open (at least right to distribute binary drivers and firmwares) and that's all.

I'm coming from openmoko community, a community that's alive even if openmoko Inc. left us with very little support.

Just have fun and enjoy your N900. Software can be changed, so don't worry about it. Nokia is not a vendor that closes up thair devices.