It's not a question of where to promote as long as Google is not banning Bitcoin mixers and the authorities are not requesting or instructing domain registrar and hosting to host these Bitcoin mixers they will continue to exist, Bitcointalk is just one of the platforms out of hundred platforms like Reddit, forums and reviewers they will still have a presence, the question is how users are going to find out about which Bitcoin users are legit and are not because Bitcointalk is a place where you can discover legit websites.
There are so many fake mixers on the internet and Bitcointalk is a place where they expose, because this is a discussion community but their presence will still be felt because it has a huge market