..Hynix originally planned to ship HBM2 in Q3 2016 but it was pushed back a quarter in every upate since then. The company initially planned to introduce two HBM2 products, rated at 2.0Gbps and 1.6Gbps. Overtime, the 2.0Gbps product was ostensibly scrapped in favor of the slower memory, likely because of yield/cost challenges...
According to AMD, the first Vega GPUs will be for professional use and cost a lot. Those are the ones being released in June.
According to AMD, the gaming Vega GPUs will be cheaper and fast for gaming. But, the gaming GPUs are coming out later this year (they were supposed to arrive in 2016).
The reason gaming Vega is still not released is delayed Hynix HBM2 memory -- not delayed Vega GPU chips. Quantity production of HBM2 is already delayed 9 months and is pushing a one-year delay.
AMD "took a chance" when they designed Vega for Hynix HBM2 memory that did not yet exist. Taking that chance did not "pay off" and is costing them the better part of a year.
Nvidia did not take that chance (they continued to use conventional memory). We now know why Nvidia has released their high end products so far ahead of AMD (delayed HBM2 production by Hynix).