EDIT - When will the res of the campaign continue does anone know ?
I have understood that the campaign is very likely
not to be continued. But I hope I am wrong. But it's better not to wait for it to be continued. All signs indicate that they are not working on it.
As what comes to the winter missions, there are great multiplayer winter missions. You can dig them out from the FDF Mod mission repository. You can play them as single player too, just make a host on your own machine and take a squad leader's position and keep the other team members as AI to help you out.
I can recommend for example the mission
New Years Day by Warrior Xâ„¢, it's a good one imho.
There are also many single player winter missions in the FDF Mod mission repository.