Been hearing this for a long time and looks like it is happening. Just left my paint store and picked what may be my last quart of oil based porch and deck enamel from my supplier. She was telling me one of the companies is pulling the quarts off their shelf. Another no long has the oil based any more. She is running out of suppliers and that in a few months she will not be able to get any.
I am sure it will be available from other sources for a while, but it's going to get harder to get. And you know where this will end up. So if you building soon you might want to think about buying you paint ahead of time.
Latex works, but I don't like it much.