Can you point to a case even vaguely close to this fact pattern?
Per this posting from a law firm [1], as your question is stated with the inclusion of "might" the answer is yes. Apparently it can go one of three ways: abandoning, not impacting/abandoning, or diminishing. Two of these results are bad for the trademark holder.
I'd assume a C&D letter would be sufficient to get a proper result or at least should be the first move in these matters, but I'm not a lawyer nor play one on TV or online.
[1] https://www.dbllawyers.com/can-lose-trademark-rights-dont-su...
https://en.wikipedia.org/wiki/List_of_generic_and_genericize...
You don't necessarily need to sue competitors for being misleading, but you do generally have to show you are trying to defend your trademarks and a lawsuit is a nice expensive papertrail.
Can you specify a single one that you think is similar?
https://www.google.com/search?q=failure%20to%20protect%20tra...