I'm a bit more positive regarding CGCC
Do we stick with what we have?
I say yes.
Recent events with SE Inc. have been very unfortunate. I see reasons to disagree with the company, and how that can lead one to cease being a moderator, or to volunteer time for them.
But that doesn't mean we should leave this community. When we post a challenge, answer, or discuss in TNB it's not for the benefit of SE Inc. We do that for ourselves, for the community. And as for the questionable rules that are being imposed like the new CoC and the pronoun stuff, personally I haven't had any problem so far just ignoring them and following the "be nice" principle.
I like this community. I have met some really clever people here, had many interesting conversations, and a lot of fun. I would like that to continue. And I think it has to be here, not elsewhere. As I argued in another answer, there is no moving to another community. It would just be a parallel community, with a different culture, competing with this one. And I don't see how the new community would be better than this one, or even viable.
If we are to stay:
What are we going to do about getting new mods? I mean, I don't know how much @Doorknob can handle on their own.
I would see that as a problem of the company, more than a problem of the community; but of course the community would be impacted by not having enough moderators. I guess SE Inc. would intervene. Maybe staff would do some minimal moderation.
I don't really know.
Update: A site could be shut down if there are not enough people to moderate it. With that knowledge, I think people may be more inclined to become moderators than they have shown here.
Will the best of CGCC 2019 still continue?
Yes, if we want. That doesn't require a lot of moderator intervention anyway. Nominations, votes and bounty-awarding can all be done by regular users.
What happens if more people leave?
People leave and people come, all the time. As long as there's a reasonable amount of people the community can go on.
If we are to go:
How long would building a new community take? I mean in terms of site reputation, community feel, resources, and getting it to the point where it is feels like CGCC
It would take long, and there's the problem of making it all viable (financial support? Volunteer work?).
What happens to CGCC?
It continues to exist and competes with the new community, appearing first in search results, and probably attracting more new users than the alternative community, at least in the mid term.