About season 4...

The season is set to be a full one. Prison Break will be on in the fall, take a break (during which Dollhouse and 24 will air), and then in late spring Prison Break will return to finish Season 4.
Michael’s tattoo will be addressed in the first episode.
Due to all of the plot lines, Sucre will now be a combination of his characters in all of the Prison Break seasons.
Michael Rappaport will be more of a supporting character this season.
The relationships with Mahone will be interesting. “There will be times when there might be some conflict but Michael and Mahone have an understanding and a hesitant respect of each other and what the other can do. Lincoln and Mahone will be more interesting but they may even find something to bring them closer together.”