My only potential hang-up with respect to the "visibility" of the coaster track is that I think lots of bare steel jutting up from the ground would be an immersion-breaker unless it's justified as part of the story and reality of the ride itself (and isn't that the reason Rowling had been wanting to see Dragon Challenge replaced?). We can see the track, for instance, on things like Big Thunder, Seven Dwarfs, and Everest, but the story of the ride accounts for that by placing us on trains or mine equipment. Ditto for Gringotts, which places us on the railed conveyance used in the actual environment as depicted in the books and the movies.
We all know we have to suspend disbelief to some extent when we get on any theme park attraction. I've got no problem with the prospect of being able to see our coaster track in front of us, but I hope it's going to be very well themed and incorporated into the environment in a more cohesive way than just a standard coaster would be.