Somehow, I don't think the future is too bright for Miguel. I can see it coming to a point where he's basically lining up victims for Dexter, until his own personal interests take precedence over "the code".
Like, asking Dexter to kill off that eyewitness that can apprently absolve that guy he prosecuted (name escapes me at the moment), but lying about the circumstances. I can see Dexter finding out about it after the fact, and deciding that friend or not, Miguel's motives aren't in line with his own.
I agree that it would be great to see Dexter finally find someone with whom he can truly be himself, but that would impact upon Dexter's constant struggle with his "dark passenger", and would suck the life out of the show. Sadly, for the show to maintain its drama, I think Miguel Prado has to die.
I hope I'm wrong about this, but I guess time will tell.