Bioware tried the win only quest system for normal PVP before and it resulted in people abandoning warzones they can't win in large numbers. How will arenas be different?
Once I get my 1500 rating and I am guaranteed end of season rewards, what do I risk by quitting arenas I can't win in order to complete my daily/weekly?
If you leave a ranked match you lose rating in addition to not getting the reward. If people are leaving that is just the type of person that they are. Incentives probably aren't going to change a douche.
They are going to be holding out the rating needed for the new season so that it may be even higher than 1500 this time around.