True but I still feel solace that nothing besides the heat death can destroy the entire universe. In that sense we will have left a mark of sorts. The collapse into the false vacuum might even be the start of a new universe since it would liberate so much energy. You could get Kugelblitzs forming possibly. It's hard to think what the new rules would be because so much is dependant on that one tiny thing. What I do know is the speed of light wouldn't change that much.