When it dies go mine a newer coin, there are plenty of altcoins to mine with a GPU, although not as profitable.
And the other 2+ million GPUs will be doing the same thing, KILLING most or all profitability on most coins since all other GPU-mineable coins COMBINED have ballpark 1 million GPUs mining on them.
Better have REAL cheap power at that point if you want to make anything.
The way profitability is going, due in part to the large DROP in coin pricing over the last couple weeks, we might not get TO that point on ETH.
Folks with high enough electric costs are ALREADY getting squeezed out of GPU mining for a profit, and I've noticed that network hashrate on ETH seems to have flattened out a LOT the last couple days (it's not QUITE stopped on growth, but pretty close).
Yes, I can see this turning into another version of the 2013 "boom" 2014/2015/2016 "bust" cycle in GPU mining.
One would need another pricepump of Bitcoin to drag along most other altcoinprices upwards to be GPU profitable for those with the highest cost of electricity. ETH is still good to mine though atm.