What also would be interesting: Can they change with an ethics shift in an ai empire? We do know the player may do this. But is it also possible that other empires change there ethics? I am not sure but I think I read something about the player being able to influence other empires (either directly or indirectly based on his actions) over time (not the primitive indoctrination thing) so in that case a shift of empire personality would also make sense.
This was kind of my thinking about this - so could 'honourbound warriors' become 'hegemonic imperialists' if they move to being more xenophobic, or is there even a need for AI personalities anymore if ethics dictate playstyle?
If not the latter, I'd be curious to know if ascension perks are tied to ethics or personalities - so would a hegemonic imperialist more likely to persue a supremacy / domination perk over others or would your military ethos dictate this?
EDIT: Personally I'd like it if personalities dictated it. It opens up more options for specific empire playstyle, where two could be functionally similar, but could be achieving different goals. (Such as evangelising zealots gunning for purity and prosperity perks, whereas spiritual seekers would go for prosperity, and attempt to make contact with the shroud)