Unless it's urban myth, SFA has a height ceiling at something like 200', so chances are it wouldn't go there. Plus it's a huge investment and you have to be sure you get your money back and make a profit from the project over X years.
Is the 500-foot barrier even worth it? It'll have to be a tophat like TTD and KK, which cost $25 million at lower heights so certainly the higher height mark would cost more.
Or I guess it could be a launched shuttle like Superman: Escape from Krypton, which I guess would be cool...?