Inferno faction discussion.

It seems there is official information that Juggernauts are a replacement for demons (i.e., the 2nd-level unit), and they will leave Devils as a tasty treat.

There is a lot of conflicting information about this on the internet, but on the Heroes Corner, Juggernauts were reportedly named as a replacement for Devils, although it seems that only the developers know for sure.

In any case, in the trailer, they look quite large compared to a human, so I think this monster in the picture should be at least a 2nd-level unit according to the new classification.