This "news" is no surprise to anyone who's followed the Cubs' radio moves over the last year. When they signed a seven-year deal with CBS Radio to begin in 2015, they had the right to opt out of being carried on all-news WBBM 780 and move to WSCR 670 ("The Score") after one year.
That's now exactly what they've done, according to longtime Chicago media writer Robert Feder:
Chicago Cubs baseball broadcasts will air on WSCR AM 670 next year, according to a joint announcement Wednesday by the team and CBS Radio. Confirming a report here last month, the Cubs will shift to the sports/talk station from all-news WBBM AM 780, where they aired for the past season. CBS Radio had a one-time option to move the team to The Score, under terms of its seven-year rights agreement. "We are excited to continue our partnership with CBS Radio and join Chicago’s top sports station," Crane Kenney, president of business operations for the Cubs, said in a statement. "With the broadcast team continuing to deliver great coverage, our first year with CBS was outstanding, and we look forward to many more to come on WSCR."
This move became possible when White Sox games, which had been carried on WSCR for the last 10 seasons, moved to WLS 890 in a new six-year deal.
WBBM was never a good fit for the Cubs, squeezing baseball broadcasts in between traffic and weather and not having any time for other baseball-related coverage. An all-sports station like The Score will allow the team to develop pre- and post-game shows similar to what they had for many years on WGN.
For you the listener, nothing will change except for pushing a different button in your car, if that's where you listen, or tuning to a different frequency on a terrestrial radio... which is something few people listen to these days anyway. I'd guess most baseball radio broadcast listening is done online or via the MLB At Bat app. All the current broadcasters, Pat Hughes, Ron Coomer and Mark Grote, will move to the Score.