I think Bitmain maybe getting close to their cost of production.
Increased difficulty combined with a falling BTC price can lead to a situation where it no longer makes financial sense for a hardware manufacturer to produce another batch of hardware.
If the price of BTC falls further or remains close to where it is now, I expect less mining hardware to be produced in the near future.
Nothing new here. Remember the 333MH/s block erupters? They were like $150 or something in the beginning and in the end just a few dollars. Then they stopped making them because, like you said, the production costs were higher than they were sold for.
However, if you produce a new chip (a faster chip and perhaps also better power efficiency) you're all good to go again to follow this same route.
Pure theory here, but what if Bitmain is able to produce a chip which is twice as fast as their current chip and they're able to run it in the same configuration with hardly any extra costs? Then you have a miner which is capable of 360GH/s at perhaps 500w and it's all good to go again for the next months.
So it's not like less mining hardware will be produced, but there will be less mining hardware of this current generation produced and they'll move on to the next generation.