Good question. This is a bit different as this is the first time there's an existential threat to witnesses. There are many ways to merge Steem with Tron, but one way listed in the original announcement is simply moving all dApps, tokens and infrastructure (including Steemit.com of course) straight to Tron. If that happens, Steem witnesses will effectively be made redundant. So, they have much more motivation to do something about it than ever before.