They of course could keep on working on CM in general, and do contracting for other people as well, but at least your phone would have CM support out of the box.
I imagine the CM people could organize a bit to facilitate such contracting, but I suspect the reason this hasn't already been happening is that there just isn't really any demand from the manufacturers. I can't really say I know anything about the industry at all though, so I might just be talking crap.
Thanks for the answers and I'm happy to see that samsung did that. I know for a fact, that if I was a company and someone was making MY product better....for free, that I'd be offering them a job. That is the kind of employee I want in house, self motivated and creative.