Newegg has listed NVIDIA GeForce RTX cards ahead of a probably announcement at today's "BeForTheGame" event in Germany, apparently confirming the rumors about the existence of these two GPUs. Both RTX 2080 and RTX 2080 Ti cards are featured on this Newegg promo page:

Clearly this went live a bit early (none of the linked RTX products bring up a valid page yet) as NVIDIA's announcement has yet to take place, though live coverage continues on NVIDIA's Twitch channel now.