Q: Does MacBook air have air play?

About AirPlay and Airplay Mirroring

AirPlay Mirroring requires a second-generation Apple TV or later, and is supported on the following Mac models: iMac (Mid 2011 or newer), Mac mini (Mid 2011 or newer), MacBook Air (Mid 2011 or newer), and MacBook Pro (Early 2011 or newer). For non-qualifying Macs you can try using Air Parrot.

Several Apple Articles Regarding AirPlay

Apple TV (2nd and 3rd gen)- How to use AirPlay Mirroring

How to set up and configure AirPort Express for AirPlay and iTunes

About AirPlay Mirroring in OS X Mountain Lion

iTunes 10- About playing music with AirPlay

Troubleshooting AirPlay and AirPlay Mirroring

Using AirPlay

Thanks to the $15 Beamer, AirPlay streaming is still possible on Macs  that do not support Airplay and mirroring.

Another solution is the Air Parrot.

Mavericks will be available for purchase and download in the Fall.

OS X Mavericks

You will find all the public information about OS X Mavericks here: Apple Releases Developer Preview of OS X Mavericks with 200+ New Features.

We are all users, too, so we don't know anything more about Mavericks than you.

For more information on the features of Mavericks see: Apple - OS X Mavericks.

Mavericks is expected to be released sometime this Fall.

Its against the forum rules to speculate on FUTURE OS,.......

but Apple DID SAY in its recent keynote speach that the new AIR was  (as i recall they said it)  "designed to be ....perfect integration.......with Mavericks OS".