I stated this on the Screenz thread; and i'll state it again.
I am in the camp that I think that they will make changes to F&F that will accommodate more practical effects, so its not as bad (Aka, get robotic cars into the 360 room). Musion, in my opinion; will be a major factor to Supercharged, and not Full-screens.
Especially looking at USH, the only two scenes that had a major screen presence was the Musion room (which featured the rising semi truck) and the 360 room (with the curved screen). I would think that because of the possible delay, its to help allocate time to incorporate the use of new actors from Fast8, and to rework the entire 360 room to accommodate robotic effects (Helicopters, Cars). That way; the attraction doesn't have as much of a problem as some people fear.
I also want to add, that I think that the line will be very much of a "Lets change things out every two years"; so that way, they can incorporate more cars from future installments (it'd make sense too when you think about it, synergizing the future films while getting repeatability for fans of the franchise). That way, it can cover for the probable lack of practical effects in the line.
Incorporate two-scenes (Musion oriented with practical effects) before what Hollywoods preshow was, the preshow from Hollywood (updated to accommodate Ludricis and maybe Scott Eastwood), then having the new 360 room feature not just Luke Evans, but Jason Statham to the mix, and then one new final goodbye scene with Scott, Ludricis, Tyreese, Dwayne, Michelle and Vin projected onto a musion set.
It'd make the ride up to date with the series, while allowing changes to accommodate the area (and as stated, 360 room to update in its size to accommodate robotics). I think that should be the best option, if they aren't re-working it to act much more like the Gringotts/Mummy system. You wouldn't really need 3D too, in a strange way; but that's my opinion on what I think should/could be the case for Supercharged, so it doesn't piss everyone off.