Doesnt Sylars power work by allowing him to understand how others powers work? If that is the case, and Matt wiped all of his memories, then none of those powers should work anymore. In theory that is. I mean genetically he should still have his orignal power, and probably Nathan's power because he still understands all about Nathan, but the rest of the powers would be gone. I guess there are big story flaws in that line of thinking though as if he lost all of his other powers he wouldnt have been able to still shape shift to look like Nathan. We have seen that the writers let little things like that go anyway.
The other thing is that in the graphic novel that came out after the episode it states that Parkman replaced Sylars mind with Nathans. If that was the case then Sylar should really be gone, but Nathan could still become physco and become like Sylar if he ever learned the truth.
