Keep in mind that it doesn't have to be an Hispanic media company that buys the stations. It can be anyone. It could also be a group of executives from within these stations who see the value in the stations they run, and have access to the money it would take to buy them.
In the case of Univision, they already sold a group of their AM stations to an Hispanic media organization, and we've heard there were other groups who had interest in those stations. So it's very possible that the same group that bought the AMs might be able to get financing for the rest of the group, or buy even more stations. Or that the groups that lost out on the AMs might put together an offer for the larger group.