Shaggy punching Dickbag Superman in the balls would be fun, honestly.I know a lot of people don't like guests, and the NRS 2-year support/release cycle is frustrating for those who want longer support, but I can't argue both are smart and work well for them. The guests sell well, and people are super hyped up for the next game in the MK/Inj series 4 years after the previous one. They've got a good thing going, and I can't really see WB wanting them to change it up.
I know it's a meme, but I could actually see it happening for Injustice 3.