Second whacked out theory – the beans don’t open portals but Wormholes to other worlds. Worlds where science and magic are a medley and time passes differently based on the planet’s distance from the sun.
So Storybrooke is like a permanently opened wormhole that is about to shutdown. Thus there are infinite worlds to travel to, not dimensions. This opens up the possibility of other franchises that Disney owns, which I believe Star Wars is now one of.Though I doubt that would happen soon.