Although I think that the best scenario for the rest of the season would be for the skinner to be Miguel. Some how it seems too obvious. It seems like a set up for a twist toward the end of the season. Joey Quinn has been a pretty unimportant character but he seems to be in the middle of everything. He has his shady past with Yuki and that's pretty much all we know about him. For someone who hasn't been a big part of the story why is he in the middle of everything, I think there is a big reveal coming and don't be surprised if it has something to do with Anton.Something to me seems a little fishy with this guy(Joey Quinn) and I won't be surprised to see him get a bigger role in the upcoming episodes.
I will say though, that Miguel being the skinner would also be great for the end of the season. Like an earlier post said, it would end up with a great face off with Dexter in the last episode. Whatever happens, I'm sure we'll be in for a treat.
So for the record. I think the skinner will end up being Joey Quinn. Miguel seems way too easy for this show. Plus if he was the skinner, why would he try so hard to get Dexter to do what he was already capable of doing, unless he knew what Dexter was, which opens up another can of worms.