Eh, I don't think this is a big deal, like at all. It's pro wrestling, accidents happen. Punk is not paralyzed, and his neck isn't broken, so life will go on. And I'm a big fan of the guy, but let's not kid ourselves here. Punk has had a few incidents in the past. I don't remember the year or the name of the pay per view, but I do remember an incident, where Punk bloodied Mysterio's nose after a GTS. And if you watch the slow motion replay, you can clearly see Punk's knee slam right into Cena's jaw at MITB 2011.
As far as Miz goes, well besides the segment with Lesnar last week, he hasn't set the world on fire during his face run. Plus, Lesnar deserves a lot of the credit for the success of that segment, because he's easy to hate, as the big bully. In fact, Miz started to cool off during his feud with Alex Riley, after losing the WWE Championship to Cena. So Miz wasn't on the path to a world title reign, or a match with The Undertaker at Wrestlemania. He was just kind of there, so heat or no heat, Miz wasn't going to suffer some colossal setback, because he hasn't done anything worth remembering in two years. Maybe this incident will slow his momentum down a little bit, but I don't expect him to fade away into obscurity.