At least Google released a final version of O3D that was an implementation on top of WebGL, providing a transition path. When they dropped Gears, they said they said,
We realize there is not yet a simple, comprehensive way to take your Gears-enabled application and move it (and your entire userbase) over to a standards-based approach. We will continue to support Gears until such a migration is more feasible...[1]
How did that turn out?
They filed a Chromium ticket[2] that was moved to an html5rocks.com ticket[3] four months later that was closed as WONTFIX a month after that.
My issue is not that they discontinue projects. My issue is how they often go about it.
