Airbus currently mixed 330/340 - all pilots are mixed fleet. 350 replaces the 340 so mixed fleet will change to 330/350 for all - bit of a changeover period I guess but I suppose 12 months max maybe. Yes 330 guys are busy at the mo but in days of old airbus had the best routes and no doubt things may swing that way again/or back/or forth/or somewhere who knows
All I know is I like working there.