My US friends told me about this. I am 2013 EB2 PD and living in Canada for 3.5 years now. Here are some reasons it's not a big deal for me:
1. No guarantee that Filing Date will be honored next month.
2. No guarantee that my employer would have cooperated in downgrading
3. No guarantee the downgrade could have come through in a month
4. EAD is great, but its NOT a GC - you still need H1B to be safe, you need to renew periodically and not be jobless when renewing
5. Time spent on EAD doesn't get you any closer to citizenship (I want a 1st world passport to travel, EAD or even GC does not give me that). Such a passport is no use if I have to wait till age 45 to get and I feel too old and tired to travel.
6. Similar thing happened in 2007 and 2012 and date retrogressed...so people were stuck on EAD for almost a decade without getting GC...can happen again.
7. If I really want to go to US, I can since I already applied for citizenship in Canada and dont really need to live here to maintain RO anymore (barring exceptional circumstance where citizenship takes 3 yrs to process). I am still H1B cap exempt.
8. Unless FAD goes to 2013 and stays there for more than a year, I don't lose my PD...so no hurry to go back.
9. Even if FAD goes to 2013, my spouse's PD is in 2015, so I have another shot later.
I am happy for my friends in US, they (might) get something after spending a decade in US, some kind of partial stability.
Would I have moved to Canada had this happened 4 years ago? Answer for me is - yes. EAD is like a small bone thrown at me. Nothing short of full GC would have kept me in US. US immigration occasionally throws bones like these to Indians to keep giving hope only to dash them.