Nope. It depends on which game you are talking about, but there are other ways as well.
In Black/White 2 Pokemon in Hidden Grottoes would have their hidden abilities.
In X and Y Pokemon in Hordes and in the Friend Safai's have a chance of having their hidden ability.
Some event Pokemon also have their hidden ability.
There might be other ways as well, but those are the ways I can think of off the top of my head.