There will be a new rewards balance on each account, much like your normal balance and savings balance. So 3x "balances" for each liquid currency.
All rewards will be deposited into this new rewards balance, which will then have to be withdrawn in order to transfer.
The reason behind this change I've been told is for scalability, though I'm not 100% sure how changing which balance it goes into accomplishes that.
RE: [Poll] Your Opinions on Hardfork 17 Features