Here is the link, is in spanish. Basically, Manny Paquiao offer a 4th fight in Mexico, Manny had trained in Mexico to get use to the climate. Later this month, around the 21th the announcement is going to be made.
http://espndeportes.espn.go.com/news/story?id=1608380&s=box&type=story
Well Pac called it after the Bradley fight, during that interview that he would like to do it in Mexico. Wouldn't be surprised if it's both their last fight.
I think Pacquiao would like to fight him in Mexico but Arum would be against it. Anyway Pacquiao's next fight is in Vagas. To prepare for a fight in Mexico City it's a good idea to train at a high altitude because you will be fighting at almost 8000 feet.