My initial reaction was pretty much the same as everyone else.
"Hardware review site says don't wait for hardware reviews, buy now."
Then I sat back for a second and thought about it. I still disagree with the sentiment in general. But, I do sort of reach a similar conclusion. Just, for completely different reasons.
If you bought a 1080ti the moment it came out, you had the fastest consumer (ignoring Titan here) GPU in existence, and you've had it for over 2 years now. Until RTX cards ship at the end of September, you still have the fastest card. So while it's never going to win the value proposition, from the perspective of wanting the latest and greatest it's had one of the longest reigns of any modern GPU.
Looking ahead to future generations, the release cadence has definitely slowed. I'd be pretty surprised if AMD can match a 2080ti anytime soon. The next process shrink doesn't seem likely until at least 2020. And Nvidia probably won't do more than a refresh in the next year. So given all that, in terms of longevity (such as it is at the bleeding edge) if you always want the fastest card then the 2080ti is likely to be top of the heap for quite some time. If that's your criteria then waiting isn't going to serve any useful purpose.
But for everyone else who actually cares about value, of course wait for reviews and benchmarks. Who knows, maybe it'll be like adaptive refresh. It doesn't improve fps at all, but people seem to like it nonetheless because it can make games look/feel better. And Freesync, G-Sync certainly don't get the kind of hate we've seen directed at Ray-Tracing so far.