It seems that there are plans to remake Metal Gear Solid using the Fox Engine. This was announced by Kojima during an E3 2013 interview in response to a fan question.
Kojima said he is in the process of looking for a studio that can adapt the first game to the Fox Engine, noting that some of the mechanics would need updating.
Kojima talked earlier about putting an outside studio on remaking Metal Gear Solid, but this is the first time he mentions the Fox Engine. In any case, plans for it still seem to be there.
Source: Game Reactor