Hahaha! Yeah, well it could very well turn out to be wrong but here goes...
I think the new "main" bad guy will turn out to be the same British guy posing as Kensei in 17th Century Japan. Why do I say this? Well, mostly it's just a strong hunch but there have been some hints. Most notably in the latest episode after he is shown healing, Hiro says "Godsend". It then cuts to a scene with Molly with the first shot being of one of her drawings of the villain's eyes with the Godsend symbol.
Also note, while he appears to be a jovial chap he hasn't really expressed any heroic aspects whatsoever. On the contrary, he's quite obviously vain and self-centered, which is the starting point for many classic villains.
My hunch is that he not only has these healing powers (like Claire) but also does not really age and is still around in the present day of the story. Perhaps he was the first person to have Special Abilities and established The Company but was ultimately betrayed by the rest (including the Petrellis, Linderman, Nakomura, etc) when they discovered his true nature.
Again, it's just a hunch and I could be way off. But I've read so many comic books, graphic novels and basic mythology that this revelation would not surprise me in the least.
Also, I don't think he's really the historical Kensei from the show's mythology, either.... that is obviously going to turn out to be HIRO himself.
I initially thought the same thing about the baddie being Kensei after the first episode but hope that is just a bunch of red herring clues because it would be way too obvious with the clues they have already thrown out.
Also, the Hiro being Kensei theory has been floating around since last season and is already playing out to be true.