There will be a physical release of FoV for PC, but not Xbox. There will also likely (I assume) be a download releases on PC, but FoV is too large for DLC on the Xbox.
Both platforms will get a physical release of DKS, the combined D2:ED (remastered, with changes to the flying fortresses the main difference mentioned so far) and FoV.

Larian may need to wait until distributors have been announced to determine / answer whether FoV requires a similar distribution of D2:ED. I don't have Steam (etc), so I'm not sure if download add-ons in general are compatible with retail versions of games, as the original poster was asking about.