I know they aren't going to be in the Everglades - it was hypothetical. Wherever you introduce them, they're going to hunt certain animals in the ecosystem to the point of extinction - a lot of which are already endangered or struggling with their habitat. Do you really want keystone animals being hunted to extinction and screw up the environment they're introduced to beyond saving?
I don't like when amoral scientists play God with the wellbeing of animals; this is exactly what Michael Crichton warned us about. Just because you can bring ancient animals back from extinction doesn't mean that you should.
They're extinct for a reason, and they died out naturally, unlike certain animals who died because of human interference that could legitimately have a reason to be brought back. Let them rest in peace.