The biggest problem with OpenSolaris was proprietary blobs required to build it. Do you know if Fuchsia has any of those?
If it doesn't, then just fork it.
If it doesn't, then just fork it.
Forking is always easy, maintaining is hard. Also, we're not sure whether things will be made harder by Google when things get mature.
I don't have any Android devices, and I don't follow its forks, derivatives or general state too closely. If you have the money and the means, you can always make a fork of an open source software and make it work for you.
To be more accurate, maybe I can say it won't be very useful for the general public, but big companies can do whatever they want since they have the money and the man-hours.