I'm of the view that the existing card line up will probably be the shortest lived GPUs in Nvidia's history, before we see new ones. The whole range just makes so little sense from a cost/performance stand point, yet this feels deliberate in order to clear out Pascal stock. Add to that the abundantly clear fact that even a 2080Ti isn't the all singing and dancing ray tracing solution Jensen made it out to be... not even close, and forget the 2070/2080, they aren't even in the ray tracing race... and it all points to these cards being a stop gap before 7nm lands. Given AMD are already far down that road with such products imminent, I feel it's fairly safe bet that Nvidia won't be that far behind.
They will have about a year before NVidia and AMD 7nm PGUs come along, and its not clear if either companies offering will aim to take on the high end until 2020.
Even at a year, that is a long time by traditional standards. There used to be a new GPU every 6-12 months.