It’s far from official, but the South Korea NT wikipedia page has a second friendly in the US listed for January 25. The location is not listed, but the opposition will supposedly be Costa Rica. That would be in addition to the Jan. 29 friendly against Mexico in San Antonio. Don’t know if it’ll happen, but watch this space.
Also, thank you to Tim (Korfan) who brought to my attention that the friendly against Mexico has been confirmed by FIFA (it appears on their website).
Also, in a Korea Herald article, they wrote that the plan is for Korea to go to Brazil in early January for training, and then play three matches in the U.S. at the end of January. So, supposedly that will be Costa Rica, Mexico, and one to-be-named team.