Just wait, like always someone will make a hacked version or editing one of the .plist files to get it supported, people always do!
Just look, Siri an iPhone 4S("Hardware") only feature; Runs on Jailbroken iPhones back to the 3GS and iPods right back to the 3rd Gen.
Unlike Phones apple can't limit what we do on our computers, Il look into it in the morning and see if any compatability files can be fiddled with.
As "Loyal" as i am to apple even i thingk this is a joke.
Luckily the iAtkos team will get ML running on macs older than 2008(Just like they did with Lion and CoreDuo Macs) so that's not an issue as for airplay, Someone will figure it out as it's obviously not a "hardware" only feature Like Siri
As i said i own a non-compatable airplay Mac and a compatable one, i will look into the files in the morning and check for differences etc. who knows it might be as easy as copy and pasting something in terminal or editing a plist file-This is what apple do, and this is what we do; We fix the greedy companies mistake!