Keith Olbermann signed off for the last time on Friday, Jan. 21, abruptly ending his nearly eight-year stint as the host of MSNBC’s Countdown With Keith Olbermann. In his closing remarks, he thanked the show’s audience but only obliquely referenced his reasons for leaving. ”There were many occasions,” Olbermann said, ”particularly in the last two and a half years, where all that surrounded the show, but never the show itself, was just too much for me.” MSNBC has denied that his departure is in any way connected to Comcast’s impending takeover of NBC Universal. So what’s on deck for the left-leaning pundit? Hollywood may be calling in the form of Aaron Sorkin’s next television endeavor, a series centered on the behind-the-scenes workings of a cable news show. Sorkin spent time on the set of Countdown while writing the pilot script, and a source familiar with the project says that Olbermann may be tapped to contribute on-air rants, something he certainly knows well. In the meantime, however, his strong opinions won’t be silenced: The former host is a very active Twitter junkie.