The reason it's taking so long for the next Champ
I've seen a lot of people complaining about how there hasn't even been a hint at the next Champion. While I understand and agree that it's been far too long (one dev said there were 8 Champs in play testing...guess that means they already have three years worth getting ready at this rate), the reason they haven't hinted or released is obvious.
Look at the Champs released since Worlds patch last year.
Lucian - Broken Jinx - Too Strong Yasuo - Broken Vel'Koz - Super Strong (lack of mobility hurts him) Braum - Broken
All of these Champs have been released with severely overloaded kits that are broken half the time and have to be nerfed into the ground. Now imagine if Riot released a new, broken Champ onto the Rift right before Worlds. Hello Trinity Force change 2.0.
Riot isn't going to risk that. They'd rather keep competitive integrity (I laughed at myself writing this after the NA Regionals fiasco we have) and tweak some numbers on current Champs to create more diversity.
TL;DR Riot doesn't want to risk releasing a broken Champ onto the Worlds patch.
, the universe will balance itself and equalize the rest of the champions.