According to this story, Harold Perrineau will be co-starring in a new CBS pilot, 'Demons'. The article notes:
There has been talk about Perrineau possibly returning to the Emmy-winning adventure series, but sources said the sides could not reach an agreement.
If this show gets picked up, I guess we'll never know if Michael and Walt made it back to land.
Perrineau to face 'Demons' for CBS