it will keep getting them for a while. they've only released two phones themselves, with specs that are actually pretty close despite being a year apart, so i think they can manage pushing updates for both of them. the N1 still seems to be popular for developers too so they'd be fools to abandon it for no good reason.
Based on it's specs, it should get at least 3.0 (Honeycomb) but I don't know after that. It depends what kind of new features and requirements are introduced in the future.
I'm glad to be getting 2.3 OTA in the next couple weeks on mine but I will probably get a new phone before 3.0 hits.
I think they'd support it based on how many are still in use. I would hope they support it for at least two years, as most contracts are two years. Preferably two years after they discontinued selling it. It's not even a year since it was launched.
I think It'll still be supported for a long while. Their specs match up to about the same, google just needed something to release this year. they'll probably continue to release updates as long as they feel the Nexus can support them, which is looking to be a long while since they're really working on making them more stable performance wise.
The Nexus S and Nexus 1 will probably reach the same points in updates. They'll probably continue to be updates at least until a third Nexus is released.
I agree with this, Nexus S is very similar to the N1, so I am fairly confident that both will receive a Honeycomb update mid next year. Then come December 2011, (can't believe I'm talking about the end of the year on the first day) there will be another Nexus, Nexus X anyone? But yeah, once the 'Nexus X' comes out, I am fairly certain Google's main priority will shift to that one, and the Nexus S and One will have a stable build of Honeycomb.
I have gingerbread on my N1 and seeing its better specced than nexus s (has more available ram and better cpu) i see it supported as long as Nexus S