In fact if I was MPEG-LA I'd do exactly that. I'd work with my licensors to ensure not everyone sue at once, but rather do it all in succession. Literally have WebM in courts everyday for a decade. And remember, only one licensor need win, and they don't have to grant WebM RAND terms. They could just come right out and say, "take it off the market". And since there's no indemnification, they could in theory even go after end-users of phones, although not likely.

Of course the same can be done against H264, but it appears far less likely.

But a "flush out the enemy" strategy doesn't seem likely given the raw number of patents and licensors associated with H264.