Whither Moral Progress?
You can only answer the question if you have some sort of answer to the question, "What is moral?" If democracy is moral, then the first democrats got their walking randomly when they accidentally stepped on the "Golden path" of moral progress. Luckily they were able to recognize it as such.
Also, assuming that society would settle on Chimp rights correctly (however correctness is determined) either as human or not, is assuming your conclusion (or building an experiment that might not bear fruit until your unfrozen).