Micron announced last year that GDDR6 would be used by some Nvidia GPU with 768 GB/sec of memory bandwidth. That sort of bandwidth is surely a high end GPU, so it's probably the next generation of top end GeForce cards. But that means that such cards can't come to market in large volumes until there is enough GDDR6 memory for them to use.
Having GDDR6 memory available means that, if the GPUs are ready, we could have wide availability of GPUs that use it in a few months. If Nvidia wants to launch cards with it next week, that would surely be a soft launch for lack of memory akin to the GeForce GTX 1080 that took several months to get good stocks at near MSRP. Now that the memory is available, that won't be such a concern a few months from now.
That doesn't mean that any new GPUs will launch in a few months. But it does mean that one of the major roadblocks preventing such a launch is now taken care of. While it's highly probable that we'll see some Nvidia GPUs with GDDR6, presumably of the Volta architecture, it's not clear whether AMD will go that route or stick with HBM2 for its high end. It's also unclear how far down the stack Nvidia will use GDDR6, as with Pascal, they went with GDDR5 for their sub-$500 cards, using GDDR5X only for the GTX 1080 and up.