If I were going to guess today it'd be brave.com, but the world is large and competitive.
Edit: I agree with the sentiment though but I just trust the current situation more.
Assuming that Google is making Chromium better, sure. If they are making it worse then not keeping up with the changes is an advantage of the fork.
If Google starts making changes that reduce the value of the codebase, then a hard fork immediately becomes viable. If they are good custodians even a totally separate codebase isn't enough, it'll end up in the same position as Firefox - marginalised.
I'm not sure how much more specific and concrete you want the argument to get, but that seems fine to me. The market is big, people care about this part of it. There will be a sponsor for the work if Google isn't up to the challenge.
The only reason everyone uses Chrome is it is really good at what it does and to date Google has been a high quality steward.