Yes, the forum would still exist, though there certainly wouldn't be as much activity as there is at present.

But OP, you've apparently been here longer than I have, and this topic has been discussed multiple times over the years.  Why are you asking a question like this?  Did you miss all of the threads that discussed sig campaigns and the effect their removal would have on the forum?  Did you miss the conclusion that regardless of what would happen, Theymos has no plans on banning them?  Are you the original owner of your account?

Lol.  As I said, activity would decrease if sig campaigns and bounties suddenly went away--in fact, it would probably drop off a cliff since a huge proportion of members are financially incentivized to spend time here and post.  Look at other crypto forums that don't have sig campaigns (which would be all of them AFAIK).  Even if it's a popular coin, there's nowhere near the level of activity that bitcointalk has, and I don't think that has to do with bitcoin's dominance.

It's a moot point, though.  As I also said, this isn't something we have to worry about for now.