We don't have any support yet but from the demo's available DLSS provides some great performance increases even at 1440p.
With DLSS the RTX2080 was surpassing standard RTX2080Ti performance so the gap compared to 1080Ti once games have implemented it will probably be pretty big, or at least the potential is there.
We haven't seen the best of these cards yet.
Yes, I do believe that for the games it's implemented well in, we'll see performance jumps. I don't think RTX will be good on these cards though, so DLSS is the only tech that's interesting for me for the 2080. How long it will take, how widely it'll be implemented and if it'll be worth it is entirely unknown at the moment.
Given that 7nm is apparently close, I think that by the time DLSS is widely adopted, the next gen might well be around the corner. If this is the case, then decent resale value for the 2080 might be hard to argue for, especially those who (imo wisely) kept their 1080tis decide to upgrade when 7nm arrives.
Turing seems to me to be a reason for RTX and DLSS to be implemented in games, with future generations being built to really take advantage of it. I'd rather save my spondoolies, not encourage these obscenely high prices, and wait for NV to launch future generations at sensible prices, generations that can really leverage this awesome (but ultimately infantile) technology. Personally (and all these things really are personal, we all have our reasons and what we're willing to pay) the 2080 is in this weird limbo, not priced right for it's performance, but lacking the grunt to really leverage these demanding new technologies.
Just my tuppence.