I'm not sure they are going to be able to fall 6-8 games behind that quickly. They are only 2 games back now and there is a 10 game home stretch before the end of July. They would really have to crater for that to happen.
Since they haven't made overtures to Xander about re-signing, I assume they aren't going to keep him so I'd sell.
I bet they are just going to stand pat and make some minor moves ala Austin Davis/Hansel Robles but a very mediocre bat.