F-1 OPT expiring, I-140 approved. EAD through OPT extension or I-485?

[fc_pga 0]

My current F-1 OPT EAD expires Aug 19, which is a few weeks from now. I filed the I-140 in June; it was approved a few days ago. I'm planning to file the I-485 as soon as possible, possibly within a few days. This makes for very tricky timing.

I've received advice from my employer and school officials that I should file for my OPT STEM extension EAD concurrently with my I-485/131/765 to ensure that I maintain continuous work authorization and don't fall out of status. But I've also seen conflicting advice suggesting that the OPT STEM extension will get denied once I have filed the I-485. Is this indeed the case? Since it will be a few days before the school signs off my OPT extension package, what happens if I send in my I-485/131/765 first followed by the OPT extension petition?

While it appears that I'll have to file the STEM extension anyway (filing in time automatically extends my employment authorization by 180 days), what other steps should I take to ensure that my employment authorization does not get interrupted? I could perhaps request expedited processing for my I-485 EAD, but it's unclear if this will happen in time before my current EAD expiration -- I've read something about expediting I-485 EAD, but what are the chances that this would work?

Thanks.

Edited July 23, 2016 by fc_pga