Ever since the reformation of the Horsemen, there has been rumors saying that Mongo was going to turn on them or be kicked out of the group. Obviously, no hint of this happening has been seen on T.V. While it might be nice to see someone with a little more in-ring talent join the group, I think Mongo serves his purpose very well.
Anyways, a lot of names have been thrown around regarding who would replace him. Some of them are:
Goldberg--I read somewhere that Flair is pushing backstage to get Goldberg to join, but Goldberg wants to remain a loner
Diamond Dallas Page--I think he would be the best fit, and joining the Horsemen would give his career a bigger boost than Goldberg would get
Booker T--I like this idea, but I've also read that he is going to reform Harlem Heat with Stevie Ray
Fit Finley--This makes no sense to me
There have also been rumors regarding throwing Dean Malenko out of the group, but I just don't see that happening.