I've got to believe Bandon Dunes and Old Macdonald are the two most likely courses for the U.S. Am, because they're the two longest [in that order]. Even those are 200-400 yards shorter than the set-ups for the most recent Amateurs, so some new tees would likely be necessary, although for Bandon Dunes they can just bring back a lot of the tees that were abandoned years ago.
There's no way they are going to play different courses for the match play; it will be one of the two they used for qualifying.
When we were building Pacific Dunes and I was endeavoring to keep it short, I used to tell Mr. Keiser, "If you do ever get the U.S. Amateur here, they'll play it on Bandon Dunes." I would trade twenty years of fun golf for hosting a U.S. Amateur, anytime. I did also promise that if they ever talked seriously about a U.S. Open, I would find some more tees for Pacific Dunes, but I do not expect that bluff to be called.