I think if there would be Original War succesor, it would need the Vlaada Chvátil - the lead designer of the original Original War, but the problem is he moved on to make board games.
But there were plans for OWar 2 in 2006 as mentioned in this polish documentary, with english subtitles (on 10:30 timestamp)
You can try this mod for ArmA 3 https://steamcommunity.com/sharedfiles/filedetails/?id=905021276&searchtext=
it kinda merges the A3 & Original War and it feels pretty much like a new game, with really lot of OWar DNA, but I think its still only PvP (no AI opponent) and no SP missions