Just suppose...
What if bitcoin seems to average about 7500 USD or so over a very long period, like a year or even more. Currently, this isn't high enough of a value in USD to really mine anymore with GPU's, if mining for profit in USD anyways. I do not mine with ASIC miners and I really know very little about them, even though I almost bought a Bitmain Antiminer S9 before I build my 8 GPU rig.
Will mining taper off to little to nothing, will difficulty levels be adjusted to compensate miners, or what else?
I would be interested to know some thinking on this, should it become a reality or even close to a reality for some length of time.
That price is more than good enough for the most efficient miners to keep mining bitcoin, so we are not going to see the miners abandoning bitcoin for other more profitable cryptocurrencies, what it's going to happen is that those that have costs that are higher than that will need to either stop mining or to try to mine something that is more profitable.