If you mean The Third World War, that's going to be a reprint/update of the entire series in a single game. The Doomsday Project will be a series of individual games with the first one covering German (which is pretty much how TWW was done originally).
The scale is roughly the same, but I think TWW is more of a "monster" game than the Doomsday Project games will be. The Doomsday Project is part of their OSS series which are meant to be of moderate complexity and playable in fairly short amount of time.