The same day that Android 2.2 FroYo is announced, is the same day you can expect the SDK to go live on Google’s servers. And guess what? Here they are! Although I do doubt that mobile Android developers will be able to completely down Google’s servers by a sheer number of downloads, I do know that the SDk offers you the ability to test the OS in the emulator all the way down to version 1 .5, and up to “FroYo” 2.2.
Source: Android 2.2 SDK