There are well over 200 Emirates pilots that have applied to AA. That doesn't mean that they will all get hired or even all go but if even half go that is huge
That'll be about 2.6%, and they won't all leave at the same time, maybe over two years? That's 1.3% attrition per year. That's nowhere near huge. Europe is still contracting and will be for a few more years. That'll more than make up for that.
I think the biggest recruiting draw will be China, but there you'll trade Dubai for China. Not a change a lot will be willing to do with their families unless there will be commuting contracts in large numbers.