3 choices really:

1. If you are willing to wait at least another 6 to 8 months, just wait.
2. If you can find a better device than N900 right now, get that instead.
3. Get the N900 and enjoy all the things it can do right now and in the future.

Application support will be here for a LONG time. Especially considering N900 will support all Qt 4.6 based apps that Meego/Harmattan will run.