Interesting piece in the Tribune today about why Bob Brenly and Dan Plesac both declined the Cubs, this offseason. Apparently the Cubs deal with WGN expires after 2014, and Brenly or Plesac couldn't get guaranteed contracts past that date.
As it stands now, both Cubs and Sox play their games on WGN, WCIU, and CSN. WGN America also shows the WGN games to the rest of the country, which IIRC, they are the only remaining Superstation to do so.
What's the Sox contract with WGN? If WGN lost the Cubs, would they broadcast more Sox games? What local TV stations would make a play for the Cubs, WCIU26, WPWR50, or WCPX38? I doubt the stations with affiliate agreements would be able to carve out enough space for a local sports team (ABC7, FOX32, etc).
The only strong possibility I woul see is that WCIU26 ends their agreement to air WGN produced games and maybe air their own packages of Cubs and Sox games.
Certainly if Tribune Co was still majority owner of the Cubs, WGN would retain the team, and probably pay them below market rates for it.