You referred to FoV as an 'expansion' and 'patch', so I assumed you just had a really loose definition of 'patch'...
There will be a patch for D2:ED to include the engine and texture updates, bugfixes, etc, to get the updates that would have come with FoV if you don't get the add-on.
There may be a patch to convert D2:ED + FoV into DKS, so that PC players who have the original game and purchase the add-on can get the remastered content in DKS (altered loot, opponent placing, changed flying fortresses) without having to buy DKS (see
here).