Consider this from Bitmain's POV.  They are selling all they can produce.  They're sold out 2-3 months in advance.  What would be their motivation to roll out another version?

I don't know their exact node, but it's something 16nm.  There are several different 16nm processes.  They've caught up with what's commercially available from wafer fabs at this point.

Intel's 7th-generation CORE processors are their latest, and these are on their internal 14nm process.  Intel's not going to open their fab to Bitmain.  
AMD's latest RX 580 GPU chips are on their 14nm process.  AMD's not going to open their fab to Bitmain.  (I know, it's Global Foundries and Samsung)

Others have announced intentions to go beyond 14nm, but these are the technology leaders of the world.  It's going to be a while, and they're not likely to open their fabs to Bitmain for a while.

So what will Bitmain do?  They might consider doing a spin to a lower-power process at 16nm, but that's much easier said than done.  Lower-power processes are focused more on device leakage, for battery life while not in use.  The SHA256 algorithm flips probably 2/3 of the flops on every clock cycle, and it clocks every single one of them.  That's where your power is going.  Leakage power does not even enter into the discussion for SHA256 chips.  Maybe late 2018 for another node.  Maybe.

So what will Bitmain do?  Laugh all the way to the bank.