I see this thread has been busy while I've been away. It'll probably be locked now, but I would like to give this a swan song. In short, TWI needs more revenue, or it can't continue supporting its games. As RO2: HOS and RS aren't based on microtransaction or "endless DLC" models, a new RO outing in the Korean War would have both a ready and waiting customer base (as I've demonstrated via the popularity of Korean War movies in South Korea, a major bastion of PC gaming) and the distinction of not having been done before (so you aren't weighed down by comparisons to previous titles, and will attract more attention via breaking new ground), unlike the dozens of WWII games involving the WWII Western Front after the American intervention.
I'm sure TWI has already received acclaim over how well-made the American weapons are in RS, and reusing them (along with the HoS Soviet weaponry, and the American uniforms/helmets for South Korean infantry or entire models for American forces) should be easy, allowing for more development time and budget to be focussed on making maps and content appropriate to the Korean War time period and location. Having already created so many assets that could be reused for such a project, TWI was and remains in a unique position to create such a game with less resources necessary than a game developed from the ground up would require, a position no other game developer to my knowledge is in. It would be a crying shame if they passed up this unique opportunity or had someone else beat them to the punch.
As for those who still want to fight in WWII, the Korean War uses many of the same weaponry seen in WWII, since it started only 5 years after the end of WWII. Aside from the languages used by non-Allied soldiers and the South Koreans, you'll feel right at home firing DP-28s, PPSh-41s, M1 Garands, etc.
But the playerbase want to fight in Europe, too.
What's to stop people from saying an RO2 in the European theatre after the US get involved is just
Day of Defeat 2014 or "just stealing CoD's old thunder"? I know there currently isn't a professionally-made WWII Western Front game out right now that features the RO series' focus on tactical gameplay and teamwork, but frankly the setting has been done to death many times over by now.