CWL seems to have it's own problems. Its passenger figures manage to make Cork's look good, which is quite an achievement.
However, remembering that it was one of Cork's original 3 routes and also remembering that the rugby calendar can already provide 10-15 full flights each way a year before any other demand is considered, its continued absence is a bit of a surprise.
Realistically, only Aer Lingus Regional will operate it though and they may prefer to up frequency to Bristol rather than add Cardiff.