The resource system is gonna need a whole re-balance if they want to make hybrids competitive though. So I think that may be part of the reason it's being delayed so long, seeing as the Meta right now is single resource stacking, if they introduce Spell-crafting it'll be a gigantic ***-you to stamina builds.
Honestly I hope they allow weapon-independent resource regen before they introduce spell-crafting, such that hybrids are the way to go, and single resource stacking is solely for situational burst dps.