I never like the idea of immediate rematches, even when the first fight is a great fight. Personally, I think Barrera should retire. He has already proven he is a great fighter, and he has been in a ton of wars over the years and has absorbed a lot of punishment.
If he fights Marquez again, I think he loses again. If he fights Pacquiao again, I think he would get Ko'd again.
I think Barrera should call it quits, and Marquez and Pacquiao should have their rematch to crown an undisputed champion at 130 pounds.