Yeah, I know. From MK v DC to MK9 to Injustice 1, the community has dropped each game like a hot potato and I fully expect that to happen again.
With that said, I'm thinking long term here. What if variations die with MKX? If they don't return you're going to have an unsatisfied part of the community that will miss that sort of game. Then, you also have to take into account, the number of people that aren't in the NRS community now, who will discover and fall in love with MKX after buying a used copy from GAME or GameStop right?
Side tournaments of MK9 still happen. I'm pretty sure they did it at Winter Brawl. So even though official support has been over for that game since forever there is still a small but loving fan base for it. Nintendo hasn't touched Melee in decades, but it's at EVO because passionate fans brought that game back to life. So it's really up to gamers to decide if MKX lives on. Not NRS.
On the other hand... what if variations don't return,
but the gear system makes its way to MK11? NRS generally seems to build upon each game and add new stuff. Just like how MK9's x-ray moves made their way into Injustice (in the form of Super Moves), environment interactions made their way from Injustice to MKX, the unique characters intros from MKX made their way into Injustice 2, etc. And now MKX's variations have evolved into the gear system of Injustice 2.
Those are just a few examples of the way they keep building upon their foundations.
I fully expect the 3-variation system to disappear in the next MK game. But, in its place, I do think they will build upon this new gear system they've created, and refine it even further or make some sort of changes to differentiate it from Injustice 2. They seem to be working toward character customization pretty heavily. Who knows, maybe they're working toward a deep new create-a-character system, kinda like we saw in MK Armageddon.