If we isolate the cwnts and don't let any more into our countries, they'll have to either, get organized and sort themselves out peaceably, or get organized and try a direct world takeover bid, or they'll just slowly bomb the fwk out of themselves over a couple of hundred years.
Given their propensity for breeding with close relatives, their collective average IQ, already at a low of around 85 will drop even further, and they'll probably commit suicide by various ingenious means, at an ever increasing rate, as well as become less capable of producing viable offspring.

The odds are, that without outside humanitarian aid, they'll become extinct.