If mixers would change way they mix coins, then they would lose whole it's purpose. People who use mixers want to stay anonymous and in many cases wash their dirty money. These things obviously isn't acceptable for governments. If mixers would introduce things like KYC or similar shit, it wouldn't be mixer anymore.
I think that nothing won't change except that mixers lost place to advertise. Governments will continue to chase mixers and probably we will see more mixers getting seized.
If the mixer not earn as much as before when they were still in this forum: they might change their project or rebrand to new one into Coinjoin or P2P/Swap exchange.
I think that you overestimate power of Bitcointalk and how much it affects mixers. Forum for them was more just a place to advertise and gain reputation. But I'm wondering how many Bitcointalk members were active users of mixers. I think that main part of mixer users isn't here.