Sometimes I hear this idea about 'economic refugees' (who may be very talented or not) but I don't really see anyone like this coming to China. I think they become 'economic refugees' after living in China and realizing they aren't saving enough money to exit China and return home properly.
Anyways, I do think ESL teachers will be leaving China more often than new ones arrive. It will take a few more cycles but I do expect to see far less. Mainly due to the new disrespect for foreign teachers and the arrogance of too many Chinese employers. (undeserved).

And as for 'economic refugees' I get the sense these would be just as likely to leave - although I don't really see this distinct group. Maybe the better teachers would stay since they might have the better jobs/locations/schools in China.

Vietnam, Cambodia, maybe these will be the new destinations for ESL teachers?

You may be right... Unfortunately, Vietnam's ESL industry seems to have just as much bullshit going on as in China, if not worse. When the shitty recruiters can no longer make money in China, they will probably go there. Mind you, we hear of far less bad reviews from Vietnamese places on here compared to Chinese places.

Shame, because it is arguably a nicer place to live.