I've seen a few articles pegging the earliest release of an S11 at later in the year based on their chip purchases.
HOWEVER: I completely understand the logic of all the SHA miners being on a fire sale right now and a million coupons delivered to buyers that are worth massive amounts of money. It would all seem to point to the June announcement and immediate release of the S11.
My Guess: They're fully booted out of china, they had a SHIT LOAD of antminers running in places without a home. They hired 1000+ workers to refurb the outsides and test the hash boards, and they're selling mining equipment that has been used for quite some time but they don't have a home for.
I always figured that Bitmain had to at least own 51% of the hashpower/S9's in existence. Otherwise why sell them right? (and yes i've seen the argument regarding the profit made on selling machines, but with what they were paying for electric, i don't buy it. at all)