Any new device that bumps up the network hash rate significantly will depress the value by the same amount.
You cannot figure ROI for a new device with figures from pre-launch of that device.
It doesn't matter if its ASIC, FPGA or GPU.
Higher hashrate DOES NOT mean higher income.
Increasing YOUR hashrate with respects to the network hashrate is the only way to increase YOUR income.
This is because block creation is managed by the difficulty mechanism to produce blocks in a fixed time period.
All higher hashrate devices do is increase difficulty.
Sadly, mining is a competitive endeavour, you are competing with your fellow miners.
If you do better relative to them, you gain.
This means miners must keep up with the latest and greatest hardware or perish.
Obviously people have different budgets and more expensive hardware becomes out of reach of more and more miners.
Until people realize all this and just jump at the newest tech at any expense, everyone will suffer.
Well, at least until repetitive investment in new tech fails to improve return.
Its got to worse, before it gets better.
The only people getting rich in a gold rush are those selling picks and shovels.
Reality bites.
Sorry to put a downer on mining.

Baz