Champions for the Next Ultimate Skin

Regarding Morello's post, where he hinted who the next champion getting an ultimate skin might be by saying that the fourth letter of one of their spells is "A". I went through the champions and found the following ones that have "A" as the fourth letter of one of their spells.

Cho'Gath: Feral Scream Diana: Lunar Rush Elise: Volatile Spiderling Evelynn: Ravage Ezreal: Arcane Shift (I am aware that he has an Ultimate skin already, I'm just saying) Garen: Demacian Justice Hecarim: Devastating Charge Jarvan IV: Demacian Standard + Cataclysm Kha'Zix: Correct me if I'm wrong, but evolving his Q turns them into Enlarged Claws. Kog'Maw: Another strange one. He has a dash between words, so not counting the dash, Bio-Arcane Barrage puts him here. Leona: Solar Flare Lux: Final Spark Maokai: Arcane Smash Nami: Aqua Prison + Tidal Wave Nautilus: Titan's Wrath Nocturne: Paranoia Pantheon: Spear Shot Poppy: Devastating Blow + Paragon of Demacia Rengar: Savagery + Bola Strike Singed: Mega Adhesive + Insanity Potion Sion: Enrage Skarner: Impale Sona: Aria of Perseverance Vayne: Final Hour Vi: Assault and Battery Xerath: Arcanopulse Xin Zhao: Audacious Charge Ziggs: Mega Inferno Bomb Zyra: Stranglethorns

By my count, these are 29 champions that could be getting the next ultimate skin, some more or less likely than others. My personal thoughts is that it's going to be Diana, Rengar or Jarvan IV. Please feel free to correct me if I'm wrong or missed someone.