well think about it.  The next card logically is the vega version of the rx580 and if gddr6 is cheaper then hbm2 then yea its feasible I guess.    Problem is new tech is usually not especially cheaper, Im not sure AMD is in on that design or not like they were involved with HBM (so I guess are getting it slightly cheaper)

I expect little vegas to come with the cheaper memory types.   Someone know but I believe cheaper could also mean faster mining wise hence the perfect card