Edit: They just sold out, so at least that is promising.
I think you bring up the most important point. How many will Bitmain sell in batch 2, 3 & 4. With the A3 (batch 1 was $2375, batch 2&3 = $930, batch 4 = $520) They dropped the batch 2 price by more than half for a 40 day later delivery.
Think I am gonna wait for a batch 2 or 3 on this one. It is tempting, but I know that they will follow with more b3 miners. Many more and probably at half the price.
Probably there shall be gaps for several weeks prior to next batch to be announced (and cheaper). I doubt they will stick with current sales figures, there must be more to offer from Bitmain. Waiting anxiously.