Next-Gen Source Games with Nvidia Graphics

[FrostedSaber]

If any of the games Half-Life 3, Left 4 Dead 3, Team Fortress 3, or Dota 3 came out within the next three years, what would be the best low-medium budget Nvidia graphics card option to invest in?

Wait for an Nvidia GeForce GTX 800 series, or even a 900 series? Or would something like the GTX 760 be enough? Would want to play on high to ultra settings at 60fps, and be reasonably future-proof for the next number of years.

Would also want to be able to play Killing Floor 2, which hasn't yet announced any recommended specifications.

Thanks!

[Whatever]

The question doesn't make sense, Valve doesn't know the number 3.