Well we have ample reason to believe there were 13 antiquity civs in that screenshot (we still have not seen, by my guesses, Norse, Wagadu, and Yamatai wonders). I do not believe Mississippians are included there, so that's 14. Plus I do not believe that Teotihuacan, Nalanda, Mausoleum of Theodoric, Emile Bell, Dur-Sharruken, Hanging Gardens, or the Colossus will launch with an associated civ.
So by my estimates that's at least 21 antiquity wonders at launch, 20 if you believe Mississippians are in base game, and maybe one or two less if you are gunning for Assyria, Babylon, or Goths at launch.
That's actually a hefty number to work with for a 7 wonder cultural victory already, and as you guys have observed will get easier the more we add.