Back to the Future was made with a clause in it that Universal cannot make prequels or sequels (or essentially "reboot" or "remake") the franchise again without director/co-writer Robert Zemeckis' and producer/co-writer Bob Gale's explicit permission. In the current BTTF trilogy I have on BluRay, Bob Gale talks about that in the special features and makes it pretty clear that they have no intentions of remaking their masterpieces. Until both of those guys pass away, I don't think you'll be seeing much in terms of a BTTF remake. And until there's a remake, I doubt you'll be seeing any new BTTF attractions. My $0.02.
But who wouldn't kill to have a BTTF coaster or another updated attraction?