According to reports that've come out over the course of the week, Sin Cara merchandise is, apparently, a big seller despite the fact that the character has had little to no presence on television for the last 1/4 of this year. Vince McMahon is still obsessed about setting a Guinness World Record at WrestleMania by having the most masked fans attending a live event, or something along those lines. Vince wanted a match between Sin Cara & Rey Mysterio at WM 29, but injuries sidelined both of them. So, he'll probably try to pull it off in 2014 by having them in some sort of match.
Another report, this one I read yesterday I believe, stated the current plan isn't for Hunico to permanently remain as Sin Cara. How long he'll play the character is up in the air, but, allegedly, the plan is to ultimately call up someone from NXT to play as the character.
The Sin Cara character is, apparently, making WWE significant money when it comes to merchandise. The fact that it's making money is the only reason they haven't just scrapped the character altogether and called it a day. When it's all said and done, it's about making money. As to who could be brought from NXT to be Sin Cara later on, the guy who immediately springs to mind is Adrian Neville. Neville's agility and overall athleticism borders on being superhuman. The sorts of things WWE officials expected from Mistico as Sin Cara inside the ring, Neville can and does easily deliver. Neville's about 5'9" or so and weighs right around 200 pounds, so he's got the size. Last time I saw the guy, he was pretty tanned so he could easily pass for Sin Cara. Vince has been wanting a masked wrestler to sort of be the next Rey Mysterio, which is a major reason why Mistico was signed. While Neville isn't Hispanic, I don't think people will care as long as he can deliver where it counts. Sami Zayn is also a possibility. His physical resemblance, physique wise, isn't as close to Sin Cara as Neville, but Zayn is someone who's consistently gotten top marks from the brass since he first showed up in NXT. The fact that Zayn is also damn good on the mic would only help him out.
This is a brief clip from a very recent episode of NXT. It doesn't show their entire match, but you definitely get the idea.
http://www.youtube.com/watch?v=xju9k3s-JrY