As reported here previously, the Cubs soon will announce their new radio deal with WBBM-AM 780, beginning with the 2015 season. The two sides reportedly are ironing out final details, and WGN is not expected to match WBBM's offer.
We've heard this rumor before, and it's gone back and forth several times, so I'll believe it when I see the official announcement.
Assuming it does happen, it will end 57 consecutive seasons for the Cubs on WGN radio, which carried Cubs games as early as 1924, but only continuously since 1958. That's a long history to give up, but it doesn't carry the emotional connection that WGN-TV's coverage of the Cubs does. It's nearly certain that Pat Hughes and Ron Coomer will continue as the radio voices of the Cubs, and it wouldn't really mean much would change for a Cubs radio listener. (Incidentally, this article says the Cubs began exclusively on WGN in 1959, but I verified by checking radio listings in the Chicago Tribune archive that they switched from WIND to WGN for the 1958 season.)
If you live in the Chicago area, it simply means moving your radio dial from 720 to 780, or pushing one different button in your car. If you're listening to Cubs radio broadcasts on your computer or via the MLB At Bat app, not a thing will change, except the station identification and possibly some of the ads and station promos you'll hear. So while it's a change, the basic act of listening to a Cubs game via radio won't feel very much different at all when this contract takes effect next year.
The Cubs and Tribune Company had a longtime relationship going back to the carriage of Cubs games on WGN-TV when that station went on the air in 1948, and of course continuing through the company's ownership of the team. Now that Tribune Co. doesn't have that relationship any more, here we have a step to sever a longtime connection with its broadcast properties. We'll see if that move away from Tribune Broadcasting continues, with whatever happens with the WGN-TV portion of the Cubs' TV contract, still open for bids now for TV games beginning next year.