Basically the title. I think it would be very fitting for Faker to get a legendary skin. The legacy he has behind him and being the face of LoL Esports for almost a decade he deserves to get a legendary skin for a legendary player.
Also given that the SKT skins were released in this price order it also fits:
2013 - 750 RP
2015 - 975 RP
2016 - 1350 RP
2023 - 1820 RP
Faker was the only one in all of the winning rosters and just by his status alone he would be worthy of a legendary skin.
And then… for the 5th, he gets Ultimate skin for LB going along with her rework
money money money