Sadly, I doubt it very much. I think his de-vamper works in such a way that, once de-vamped, the former vampire can never again be a vampire. I hope he can somehow, 'cause he's actually my favorito! vampire of all time, and tu know he REALLY loves being a vampire, but.... Ah well, at least he still does have a power. And, as he says, "I can work with that."
The chances if him ever being a vamp again are very slim. Yea the fuente blood could work again but they still need to find it. I hope he can become a vamp again because it works for his character. Magnetism really kinda sucks.
I don't know...I think Helen's blood could help. I doubt she tried that, because she thought at the time that it was her blood that made John go crazy but now she could give it a try...I don't know if it would make him a vamp again, but at least make him immortal.