Is Mike McCarthy possibly the Saints next head coach if Dallas lets him walk?

Your post could be mistaken as being about Sean Payton.
Possibly, but as another poster said earlier in this thread, McCarthy has likely reached a certain 'ceiling" in his career where he's accomplished all he's going to. Perhaps Sean Payton or Mike Tomlin have as well but Payton is building a young, determined team in Denver. Honestly, even now, I still get the sense both Tomlin and Payton are less likely to screw up a winnable late-season or post-season game due to bad decision-making then what McCarthy has shown me in recent years.