About that Ultimate skin...
We know the next ultimate skin needs to be for a top-laner. But at the moment, we also need to look at the most picked vs. most popular.
Darius, Teemo and Riven would be three of the most popular. Mordekaiser, Fiora and Kench are most picked.
Now for deduction. Teemo, Riven, and Darius have legendarys. Darius has 2 so he's completely out of the question. So this leaves Teemo and Riven at least possible.
Mordekaiser, Fiora and Kench. Kench and Mordekaiser are lacking skins extremely. Mordekaiser recently got his rework, future-proofing him. Fiora hasn't aged badly, meaning no rework anywhere to be seen. Kench is still getting rapidly nerfed to oblivion to this moment, so making an ultimate skin for abilites which will be heavily altered would almost downgrade it to a legendary skin.
So the top-laner who gains an ultimate skin will be: 50% chance for Mordekaiser. 30% chance for Fiora. 10% chance for both Teemo and Riven if Riot really wants to please THOSE players.
And a 0.001% Poppy gets a legendary skin, because she's one of the oldest yordles without a legendary skin yet.