Hey Riot just curious if the enemy skins in Invasion will be released

So I have played a few games of Invasion and i am LOVING IT despite my inability to complete onslaught (yet!) and the skins that Vel'Koz, Skarner, Kog'Maw, Cho'Gath and Rek'Sai have are so awesome! If Riot has already made them, why not throw them in as 750 skins or even 1350 ones especially Vel'Koz's skin. Just wondering if there is a reason for them not being released to players.