It's the only reason I can think as to why he's not gotten a new skin in a very long time. I'm not sure what the longest 10 champs to go without a skin looks like now since some of them have gotten skins, but I've got to imagine that Zilean is near the top of that now. Is he just one of those champs where he's not popular enough to get a skin before his VU?
He's gone the fourth-longest without a new skin, after 
and 
. I also wanna note that when he got his last skin he was one of the champs that had gone the longest without a new skin... they just don't like doing skins for him.
Well they only do make a list of champs for each year that will get skins. His last one was in 2015, I mean it isn't so bad, but he should get one soon enough. They have been pushing more champs that are a bit overdue the past few years, so he could get one this year.
Ohhh you believe he will be getting a VU [zombie-nunu-tears] cute
cough SSG Ezreal came out just before Ezreal's update cough
