Well it turns out you might not have to so says the Android engineers via Twitter.
Though, we’ll be quick to point out that there is no indication of what kind of functionality, or responsiveness for that matter, that you’ll get if you want to run Gingerbread on an older device. And then there’s the issue of fragmentation — as is when will the Gingerbread update be made available for your Android device.
We know that a Gingerbread update for the Samsung Galaxy S is coming but there’s no indication on when it will arrive. So you see, even if you can run Gingerbread on the older devices, you’d still have that long wait till it is available.