I wouldn't be so sure. There are tons of contractual ties between teams and MLB. Somewhere in there you'll find grounds to at lest bring a suit. Then there's the course of business. How MLB has handled its relationships with teams in the past is an important consideration.
So if I'm McGurik, I sue MLB and drag them into a long, public, and very embarassing legal battle. I make sure Manfred knows I'd be using discovery to fish for every piece of dirt MLB has tried to sweep under the rug for the last decade. Even if we lose we'd still inflict as much damage on MLB as they inflicted on the Braves today.