I tend to think of moral values as being pretty contingent and pretty arbitrary, such that what values you start with makes a big difference to what values you end up with even on reflection. People may “imprint” on the values they receive from their culture to a greater or lesser degree.
I’m also skeptical that sophisticated philosophical-type reflection will have significant influence over posthuman values compared with more ordinary political/economic forces. I suppose philosophers have sometimes had big influences on human politics (religions, Marxism, the Enlightenment), though not necessarily in a clean “carefully consider lots of philosophical arguments and pick the best ones” kind of way.
I’d qualify this by adding that the philosophical-type reflection seems to lead in expectation to more moral value (positive or negative, e.g. hedonium or dolorium) than other forces, despite overall having less influence than those other forces.