Currently, bunkers are not covered under the Federal ADA, and I don't know of any states that have written any stricter laws.
The Fed guidelines were drafted with help from disabled golfers, who didn't feel that their access to bunkers should supercede the architectural requirements. However, its possible that in the future, some activist will sue to make bunkers accessible, with at least one flat side where his playing assistant could move the ball to a wheelchair accessible area next to the bunker.
Like you, I fear that some day, ADA could be used to require all golf courses to be as flat as an airport runway in the name of wheelchair accessibility. Or outlaw sand filled bunkers, since wheelchairs can't negotiate that surface.
For now, though, things are still very reasonable. There are features - like platform greens - that will rarely be seen again. While I have designed these, its necessary to raise the cart path to nearly green level to comply with ADA.
BTW, ADA applies to most private courses as well. Any private club that hosts outside events is considered a place of public accomodation, and thus, is subject to ADA.