well, as you can see here leagueoflegends.wikia.com/wiki… kassadin is in the list of champions which are gonna have a vu (visual update) so maybe they are having in mind to change his skills to look like that, meanwhile his splash art is how they imagine him.for example look at the latest video from riot in which we can see the new look of baron, that video is a few months old and we still didn't see any vu to the actual baron which shows that riot is sometime making the promote art (splash art, videos) for an element from their world way before the vu and from here the discordance (another example I can now think of is sion's axe)