The wait for the next batch of successful cadets start dates will be more than a year (2017 onward) anyway, last info was that people who applied 3+ months ago still haven't even got a response for their application let alone selection, i am assuming they are still finishing interviews with the cadets from last year's applicants.
Not sure why applications are still open though, definitely going to be a tough screening process.
Aside from the usual upgrades of a320 guys moving up to the heavies, i think the airbus a320/a321 NEO delays Airbus has caused Qatar is hurting the growth and plan. May be why the wait will be way longer as the initial Airbus order Qatar has already been cancelled.