A couple of weeks ago, an entry on the Hot Chips 30 symposium website revealed that NVIDIA planned to give a presentation about its next-generation mainstream GPUs. This presentation was scheduled on August 20th and would be hosted by NVIDIA's Stuart Oberman.
However, the Hot Chips program has been updated several times and the next-gen GPU presentation from NVIDIA is now no longer on the roster. There could be a lot of reasons for this, but one of the first things that comes to mind is that NVIDIA may have delayed its next-gen GPUs.
Even though Pascal is already quite old, NVIDIA doesn't really have a reason to update its consumer line just yet as there's very little on the horizon from the competition. Except maybe another refresh of some sort, there are no signs AMD is going to release anything new this year. Navi is reportedly scheduled for 2019, and will not be a high-end GPU but a replacement for Polaris.