Well, here is my perspective. Am I going to play IGAU when MKX drops? No probably not. And not because I don't like injustice. In fact I really really enjoy the game, and I'm not looking forward to going back to a block button. The fact is I work full time, I have a dog, friends and like to get out and enjoy the outdoors. I think I'm decent at IGAU because I've put a lot of time into learning frame data, character specific punishes, bnbs, set ups and grinded a lot of matches. To keep all that up while learning the mechanics and MUs of a new game, on a different console... it's just not going to happen.
When I get my ps4 and MKX comes out, I'm going to turn the lights down low, light a candle and hop on ranked one last time. Me and Selina are going to have some fun beating up on some ranked baddies then I'm going to put my copy of the game away and start learning MKX. I will do my best to support the game, and any majors I go too I'll flip the extra 10$ to play it anyways (like I did with mk9 at UFGT, and tried to do at Toryuken) just to support it for others, but for a lot of people, to play competitively at any game it takes a big commitment. Me personally, I cannot do that for 2 games.