I think it's fair to say it could be a DLSS killer in that it could offer greater performance uplift and reach a wider audience. DLSS may still end up being visually superior, especially as it ages, but the main issue with DLSS at the moment is implementation. Even if AMD are late, if they come out with something at least somewhat visually comparable, with greater performance gains, and wider implementation, that could 'kill' DLSS in the same way that Freesync 'killed' Gsync. It obviously won't just as Freesync didn't actually kill Gsync, because the technology is very good and Nvidia has its foot in many companies' doors, but Freesync as it currently is is effectively superior. It's cheaper, easier to implement, and works across multiple systems. If AMD had the financial clout and foothold as Intel, Gsync would have no place.
It seems to me that DLSS vs FidelityFX Super Resolution is a repeat of that. DLSS isn't used for anything other than gaming, it can't be used by any other manufacturer, it has to be implemented by the game developers but isn't available on the two main consoles, and it has costly hardware demands. Those are some pretty big drawbacks.
DLSS is awesome and it's in Nvidia's future for sure, but I do think AMD's answer could 'kill' it.