Michael's been recast:
http://www.soapcentral.com/gh/news/2009/0316-garrett.php


Kristina may be as well:

From Tamilu at SOC-
Speaking of S.O.R.A.S.'ing characters, a casting call is out for a mouthy 16 year old girl, and rumor has it they are going to age Alexis and Sonny's daughter Kristina. Kristina is currently played by the talented and adorable Kali Rodriquez. Her best work came when Alexis was going through cancer treatments on the show- that little girl showed some very genuine emotions. And of course, if they age Kristina, that, it would support the rumors that Michael will come out of his coma as someone who is not Dylan Cash anymore. That will make me really angry. And in turn, it would also mean that Morgan would be aged, and I love that sweet little angel faced George Juarez especially in his scenes with Jax. But hey, as I said, these are merely rumors. When I get a solid lead, you'll be the first to know.