That is actually my only concern regarding SMN for HW. BLM will be getting Astral/Umbral IV but there was no mention if SMN will be getting 4 stacks of Aetherflow instead of just 3.
If we get stuck with 3 while also having a new skill that requires a stack, I can see some foreseeable issues with that.
Logically though, we should get 4 Stacks of Aetherflow. At 20 we got 2, at 40 we got 3, at 60 we should get 4.