Just for the sake of conversation (though I suspect this really belongs in a different thread), I don't think the "well, real 2015 looked nothing like it did in BACK TO THE FUTURE PART II, so Universal can never use the BTTF property ever again" argument is impossible to overcome.
You could actually make that part of the story of the ride. Due to various time travel shenanigans, our "real" 2015 ended up looking different than the movie's version. Essentially, we're in an alternate future, like the alternate 1985 from PART II (or the other way around, if you prefer -- movie 2015 was always a weird, alternate one-off caused by time travel hijinks back in the past). The mission of the ride would then be to either stop somebody from further screwing up the timeline, or to reset things back to the way they're "supposed" to be.