I can think of 3 that have gone across to mainline in the last 2 years, and a handful to J*. All younger guys.
However, compared to people going to Cathay, Dragon,
VB, etc (non-QF group) the percentage is incredibly low (we have lost something like 50 pilots in the last 2 years - rough guess). Take that how you will.
If you want mainline, I would suggest getting a job elsewhere.