It looks like there will be a MK4, but so what? Just look at the trend.
MK1 It was just awesome. Awesome fatalities and fairly realistic violence. This was the main attraction. The fatalities were WORTH DOING.
MK2 Improved gameplay, but everyone was like, "This is too cartoony" and the violence was even less realistic, and the fatalities were a little cheesier, but still worth learning how to do.
MK3 Ultra stupid fatalities. You have to say, "Yeah, I know. This one is stupid" when doing fatalities.
UMK3 Pretty much MK3 with new characters. Fatalities were just as cheesy.

After seeing Classic Subzero's nose pinch fatality, my tolerance for stupid fatalities has completely worn away. I want no part of this trend.

If they want to market the game to 13 year olds, and phear the parents, then I'd like to remove myself from that market, and play PC games with parental advisories, like Duke Nukem 3D.