Trying to game on any Mac, let alone an air is like a three legged sack race.
You're stacking the odds of success against you severely due to the included hardware (even the GPU in a base model Mac Pro is pretty laughable from a gaming perspective), non-gaming focused OS, and form factor.
No matter what intel CPU comes out - no thin/light machine like an Air will ever be a good gaming machine because gaming focused machines will ALWAYS make trade-offs in terms of size/weight/power consumption for higher performance. Thin light hardware simply doesn't have the power or thermal headroom to game well. Whether its a DELL or a Mac or whatever.
As time moves on, the performance will continue to get higher on those machines, but the size won't change much because it will always be "as large as people will accept for portable gaming", which is already trying to fit desktop class performance into a portable.
So any thin and light will only ever be good for previous generation "e-sports" style games with low system requirements, because the high end games are a moving target.
Even my high end desktop machine will struggle with some modern titles with all the details turned on, and the video card and CPU in it were AMD's top tier gaming parts from only 2 years ago. And this machine has a CPU+GPU power budget of over 400 watts with cooling to match (I took out the second Vega 64 because multi-GPU sucks these days - spend more time tweaking settings to fix glitches than playing the game). There's simply no way you'll get anywhere close with a power/cooling budget of 12-20 watts. Or even 100 watts in a 16" MacBook Pro for that matter.
Thin/light will always be 5-10 years behind current AAA game performance.
