It's going to be 8mm, yes. It is, in my view, totally incompatible with anything that was previously released, so it's only likely to be of interest to new players or those who are happy to restart or play the game separately alongside whichever older version of Epic they play. It's also worth noting that it's going to be mostly a Titan based game, at least to start with, so it's essentially a revamped version of Adeptus Titanicus.
I won't be be buying any of it. I like my old models and playing SM2/Titan Legions, but if it does get new players interested in Epic scale gaming that's a good thing.