Nintendo's remasters of the first two Advance Wars games won't be coming this December. Instead, the company announced that Advance Wars 1+2: Re-Boot Camp for the Nintendo Switch will arrive sometime in spring 2022. According to a tweet from Nintendo, "The game just needs a little more time for fine tuning." Nintendo has "reimagined and rebuilt from the ground up," so perhaps that's why it needs a bit more time.
Source: The Verge