Releasing the Maemo 6 SDK doesn't mean that the device that goes with it is around the corner. The Maemo 5 SDK was first released in Alpha on 2009-03-02 and in Beta on 2009-04-28.

Given what Nokia has done in the past:

Maemo 1 - N770 - November 2005
Maemo 2 - N770 - November 2006
Maemo 3 - N800 - January 2007
Maemo 4 - N810 - November 2007
Maemo 5 - N900 - November 2009

It would be logical to expect Maemo 6 on the N910 (?) no sooner than November 2010.

If you can wait that long it will probably be a better OS on a better device. Of course the same can be said for the Android or Apple phones that we will see next November.