Apparently, DJMax Online is still up if your in Korea...
Gamasutra - Q&A: Pentavision's Lee Kyu Seok On Moving Beyond Rhythm Games
During the interview it is mentioned that the game is still in service, although the player base isn't that great. Plus the fact (although already addressed earlier) that Neowiz is expanding their licenses out of Korea with S4 might mean that we will be seeing these titles around the world as time progresses (slowly, but progressing)
Neowiz continues Euro expansion with new online deal // News // GamesIndustry.biz
You also cannot forget the fact that EA actually has a stake in Neowiz so chances are that these titles might be launched through them in some fashion...