Yep. Unless grandfathered and/or included in a purchase from developer, I don't see a rush of HGVC owners opting to pay it. I would imagine the same if the buy-in is similar for DRI owners.
I can't remember where I read it, but I recall reading that if you opt-in/pay the initiation, your entire portfolio is converted to HGV Max. This could be a bad thing depending on the initial inventory in HGV Max (unless you still have the normal access within HGVC).
@HuskerATL any mention of having to convert entire ownership to Max if owners join?