This is sort of just speculation/wishlisting especially as I doubt they'd actually give Ret a new resource system in addition to mana. Without deeper analysis or reason to believe speculation of this level it's not really a useful addition to the conversation.
With the arrival of real specialisation, Blizz could give Rets an other resource than mana, eliminating all the gcd-lock problems. Every ability (especially the utility ones in which I include all heals) could cost a fixed value in this new resource, or they could keep mana for utility and make the new resource for dps-abilities.
The fact that you decide to become Ret at level 10 makes it easier to implement this system, as there are no more real hybrids. Resourcecapping would also limit off-healing.