The trial is scheduled for the future. It sounds like you are blindly guessing about the case, and pretty unfamiliar with the law. Heres the case details: https://www.courtlistener.com/docket/70447787/kellogg-north-...

This isn't a "supposed law" or some new interpretation, this is pretty well established part of trademark law dating back to the 1800s in the US.

The flip side of the law is that you have to be active in defending and using your trademark if you want to keep it. It prevents the sort of patent troll abuses we see in that system.

If "Leggo my Eggo" was last used years ago by Kellogs, and they haven't used it or defended it or other "Eggo" related trademarks since then, a court is much more likely to allow the use by other businesses, even if Kellog's still hold the registered trademark.

Kellog's choices here are to risk losing or weakening the trademark as a whole, or to sue since the other party has rejected other solutions.