TVLine's Break-Up Blind Item - best f y

I’ve learned that a hit series will throw caution to the wind and put a (possibly permanent!) pin in one of TV’s most popular love stories — a game-changing move that threatens to seismically alter the DNA of the series.

Oh, and it will also piss off a lot of people, a backlash The Powers That Be are said to be fully prepared for and not necessarily all that fearful of; the aging series could benefit from having its core rocked, many believe.

OK, now for a few hints:
♦ The fandom-shattering split (which was first teased in Ask Ausiello) is slated to air in early fall.
♦ The show in question airs on one of the Big 5 broadcast network.
♦ It’s a one-hour drama.