Superman/Batman

The Superman/Batman movie was just announced. People are already freaking out. Some are overjoyed, and others are pissed off because Zack Snyder is directing. It's already gotten weird because it looks as if it's a direct sequel of "Man of Steel" and it's drawing off some of the dialogue from The Dark Knight Returns comic. Still, it sounds as if it's a license to print money.
My question is: If this was in the pipeline, why bother with the "Man of Steel" reboot? Superman is one of the most recognizable icons. There was no call for a "reboot" of the franchise, other than to erase the memory of "Superman Returns." Superman's origin story isn't really complicated enough to warrant taking half a movie to tell it, but they did it anyway and made it more convoluted and somehow less convincing. The rest was just a reworking of Superman II. They could have just released a Real 3-D update of those movies and made the same in box office receipts, and audiences wouldn't have walked away wondering about a loner Superman that kills his enemies. Superman/Batman will make infinity billion dollars, no matter how good or bad it is. The commercial tie-ins alone will make Star Wars money. The expectation is that Superman/Batman is going to lead into a Justice League movie, which isn't necessary either. Audiences don't care about the rest of the Justice League. They've been trying for years to make a new Wonder Woman TV show, or a movie, but it isn't happening because nobody can make it work (How hard is it to make a Wonder Woman film? You just put a pretty girl with dark hair in a skin-tight outfit and have her lasso things.) "The Green Lantern" movie was pretty terrible, but they'll probably have Ryan Renyolds back because he wasn't the major problem with that movie. Everyone knows who the Flash is, mostly because of Big Bang Theory fandom, and the fact that the character himself takes two seconds to explain (he's fast). Those are all the must-have characters for a Justice League movie, but they're not the ones people are paying to see. It's really just the Superman/Batman show.
It's a movie they really should have made years ago, and they almost did. Why did they suddenly decide it was time? Did they run out of coke money? Imagine the movie they could have made with Reeve and Keaton. It's an idea too big to fail. A lot of people are wary of Vs. movies like this, though, but look at Freddy vs. Jason. That was actually a pretty decent movie, and it almost made sense.
What happens to superhero movies after Superman/Batman, though? Think of how none of "The Dark Knight Rises" would have made sense in a world where there's Superman. About two seconds after Bane detonated Gotham and made his, "The city is yours!" speech, Supes would have drilled him into the ground. In "Man of Steel," Batman would have tracked down Clark Kent after General Zod demanded he turn himself over. It also eliminates the need for the separate franchises. Why waste time making a reboot Batman series, now that Nolan's done with it? You can just have Superman and Batman together fighting crime.