Flow-Walker
Banned
Maybe. But clearly there's something to putting it at the end, just for the fanboys. Plus, with the Marvel movies, it's usually just an epilogue to what you watched. A Rogue One teaser at the end of Episode VII wouldn't be the same thing you'd get in a regular trailer, but rather would be a brief scene that somehow ties the events of Episode VII in to Rogue One.
Rogue One is set in the hours right before A New Hope, more than 30 years before Episode VII.