Unlike Capcom, who had problems with MvC3 (lack of updates) and SFxT(DLC debacle); NRS could sustain 2 games. The new one would get 85% of resources and attention, but the competitive aspect that's been established this last year with ESL shouldn't be dropped from MKX just to move it to the new game. The Mortal Kombat brand is stronger than ever. If not a kombat pack and/or new balance patches, at least new skins and/or hot fixes until the next MK game. Look at the Injustice mobile game. It's been churning along with new skins and characters for 3 years now. That's impressive. They should continue using the MK mobile game to hand out skins and cards, even if the majority of people don't like it. It's a business, and the mobile games make them money.
I know people hate guest characters, but if you include a character from the upcoming game in the next kombat pack, people will get hype. Same thing with the new game; besides whatever guest character they have already settled on, an MK character should be on the DLC plans. It would also create hype if they plan another crossover at some point.
So, Kombat Pack 3 AND a new game.