MeeGo is an Operating System that might well run on the N900 hardware.

But what you bought with the N900 is a somewhat different Operating System PLUS about two dozen quite critical applications for it's usability (Browser, Media Player, Calendar, Contacts, Photos, Contacts, Phone, Maps, Camera, E-Mail, Conversations to name the most important ones).

So even if MeeGo will run on the N900, you won't yet get these apps included, because they need to be ported from Maemo 5 (GTK) to MeeGo (QT) the new OS. So just MeeGo on the N900 will look like the Maemo 5 SDK alpha/beta did: You boot up and get one or two apps...

Therefore, the critical 2nd step would be to know if Nokia's Applications for MeeGo will also support not only their next device, but also the N900 insofar the hardware or API is different. Or if there is enough information around that the community could build some of these apps. Or if they would even be open-sourced.