FoV will include engine updates (etc) for D2:ED, but AFAIK not the remastered parts of DKS.
Presumably the graphical improvements combined with the engine optimizations will mean the requirements will not increase (or they will have to add options for any added graphical features that required more resources).
So, to get all the content for PC, it's not enough to own the original game and buy the expansion, I instead have to re-buy the special pack with both?
I will probably do that, but that annoys me.