Brett over at Bleacher Nation has a story up about the Cubs surveying random fans on their opinions of WGN, buried amidst a bunch of more boilerplate marketing questions (concessions, etc). Two questions in particular, as reported by one of his commenters look to be gathering data to use in a future push for a new TV deal, as the WGN contract expires in 2014 (i'm guessing at the end of the season).
It's pretty clear where they're going with this. Frankly, I'd be surprised if they stuck with WGN after the deal runs out. As Brett points out, they can always renegotiate the deal with CSN to put even more/all of the games on that network, or buyout that deal and start working on a YES-style network. The Cubs do own a partial stake in CSN (IIRC 25%) so they might even be able to do it without much cash upfront by simply giving it up to the other shareholders (disclaimer: I know nothing about business). WGN games have already been on their way out for a while. More and more games have been popping up on CSN, and I don't think it's been that big of a problem. Generally the only complaints that I see from Cubs fans is when the game is on WCIU, which seems to be happening more frequently these days.
WGN made a lot more sense for the Cubs when they were owned by the Tribune but in today's media market the team might want to go elsewhere. They might not even be able to pony up the cash to pay for a new deal – back in the Sosa days WGN was a moneymaker for a company that was hemorrhaging money in their print business. Now that the Cubs stink and the media market is far more saturated than it was 15 years ago, I don't think WGN is doing so well. Being a 'superstation' isn't quite the ratings draw as it once was, and I remember recently enjoying (in the ACB sense) a story about WGN not doing so well financially around the time of the "WGN America" rebranding. I can't seem to dig up any stories about it, since WGN is a news organization I keep getting their general business news. I do feel much more sure in saying that WGN radio is bleeding money too, but that has more to do with how crappy all of its talk shows are.
The Cubs built a lot of their current fanbase on the back of Harry Caray and WGN in the 80s and 90s, but a big reason for it was that there weren't that many other games on TV nationally. With the caveat that this is just a personal anecdote and may not be true in general, I remember growing up in the DC area and not getting many Orioles games on TV. Aside from the relative scarcity of games, Harry Caray and Steve Stone (along with the Cubs marketing department) built that fanbase as well. Just look at how many more Cubs fans there are nationally compared to the Braves, who also had a superstation and had an incredible decade in the 90s.
As Brett points out, a hypothetical 12 year old in Ohio (or wherever) is far less likely to be a Cubs fan if they move off WGN, but at this point he or she is already less likely to be a Cubs fan anyway because there's so much more to watch these days (baseball or otherwise). If the Cubs decide to stick with WGN, they should only base it on the money, and I don't think TribCo is going to be able to offer enough to make it worth the Cubs while. The Cubs should strike a deal based on the media landscape for the next 30 years, not based on how it worked for the last 30.
I didn't talk much about WGN radio, but I think that it IS important that the Cubs stick with them. I'm guessing Pat Hughes would go to whatever new station picked up the Cubs, but WGN has one of the strongest signals in the country.