There are various arguments about how this movie will be, who will play Batman, why does it have to be "vs.", how it's not a proper Man of Steel sequel because Batman is in it... etc etc.
1. It's Batman AND Superman, who cares what the title is.
2. It's Batman AND Superman, who cares who plays Batman.
3. It's Batman AND Superman, who cares if it's not a proper sequel. If it helps, don't think of it as a sequel, think of it has a "sidequel". Did anyone think Avengers was a sequel to Iron Man, Captain America or Thor?
If you haven't checked out HowItShouldHaveEnded.com, you should. Their latest Super Cafe video is hilarious:
Peace! I'm out! I'm Batman.