The Osborne effect happens only when you know that the phone you'll buy now will not get that update. So in order to make pressure to handset makers to actually update, open development and the Osborne effect are Google's friends.
Once Google added a cool feature to the development branch, which is not really ready to use now, but people want it, only those phones will continue to sell where the update is possible. Goal reached.
Anyways, Linux distributions go to "rolling releases" or have been doing that for very long (Debian "testing"), and Google could have the same model with Android. Whoever wants the newest feature now, switches to "Android beta(tm)", and there they go. Any handset maker who wants to have the Android brand must either commit to take the vanilla Google source (and if some Chinese company does so, they should get the release-keys for free), or timely contribute their stuff to "Beta".
If they fail so, no Android brand. Google and the handset makers need to understand that a phone is now a PC, and the operating system is a separate product.