I expect that the force that will eventually promote natural values most strongly will be the prospect of encountering unknown aliens. As you say, the stakes are high. If we choose incorrectly, much of our distinctiveness could be permanently obliterated.
Stuart has worked on further developing the orthogonality thesis, which gave rise to a paper, a non-final version of which you can see here: http://lesswrong.com/lw/cej/general_purpose_intelligence_arguing_the/
This post won't make sense if you haven't been through that.
Today we spent some time going over it and he accepted my suggestion of a minor amendment. Which best fits here.
Besides all the other awkward things that a moral convergentist would have to argue for, namely: