Christine Cavanaugh has retired from the voice-actressing biz for some reason or another.
Genndy Tartakovsky is still supervising production of the show, but is not doing as much input as he used to, since he has to balance between Dexter and Samurai Jack. Co-producer of Dexter is Paul Rudish.
And according to producer Chris Savino, “We as artists have matured in taste and ability and could not make the ‘old’ Dexters if we tried. We got an opportunity to make some desired changes and we did. Much to the studio’s delight these new episodes are said to be the BEST so far.”
And Dexter still seems to be the nutty little scientist we all know and love in personality and inventions, if not his voice. Time-and science-marches on!