Realistically:
Look at the enhancements being confirmed by Nokia / done for the firmware upgrades and upgrades in the official Nokia Applications. The updates are very minor and anything which is not directly aligned with Maemo 6 or have been promised before is being done for N900.

I wish I could be optimistic, but I am not at the moment. I think Nokia realized that the N900 launch has been screwed by unfinished SW and the phone labeled as geek's device and they will focus on the next device. If N900 ever gets an update including the maps, it will be a backported version from Maemo 6.

I like N900 very much, I see no other "phone" as good as this one is, but having no OVI contacts & calendar synchronization, no OVI services integrated, no new OVI maps & navigation etc. is what N900 status is will probably be because N900 despite the huge success overall didn't break the Symbian hegemony in Nokia. I guess it is expected to happen with Maemo 6 and we can just hope N900 will be able to run Maemo 6. If so, we'll get the phone at its full potential.

Too bad my iPhone equipped friends I have teased pointing out the small resolution of their dispay have an easy shot back with "oh this is the Nokia which didn't get the maps right?" (I have heard that from one of them today actually)