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.
AA just had their first new hire class in over a decade so get in now and get your seniority number. Don't wait to be captain at EK you will just lose 60 numbers a month and what does an Emirates captain get you. 15% more work than an FO while your buddies that left for greener pastures are enjoying life.
AA has about 4000 retirements in the next 10 years. You will be a wide body captain in no time with a lot less stress and flying hours there than if you stayed at Emirates.