Nah, it's fine. They got some fairly astounding loot, but the real gift to me is that this completely shakes up my campaign's plans. As a DM, I always run the risk of figuring out villain plans early and then having to sit on them for years. When something like this happens, there's a sudden power vacuum in the bad guy plans that someone will try to fill. Figuring that out is what I love best about campaign building. They've shaken up the whole campaign, and that's just fun.
But still. I was nigh-positive I'd kill at least one or two PCs.