I'll go ahead and make this announcement now.
Mimikyu will be banned from round 2 (and all subsequent rounds).
Unresisted STABs combined with an above-average Speed and a unique ability has made Mimikyu the most feared Pokemon in the metagame. People have started running things like Scarf Beat Up Krookodile just to have a chance at taking it out early, and while these answers are mostly gimmicks, they reflect a real problem with the Pokemon. Offensive teams find themselves at the mercy of a revenge killer and late-game cleaner that puts Sash Alakazam to shame, while bulkier teams find that Mimikyu can easily get multiple boosts in a game and power through Pokemon such as Pyukumuku and Hippowdon with the power of Bloom Doom/Wood Hammer. Finally, we underestimated Mimikyu's OU usage when we were creating the banlist, and there is a very good chance Mimikyu will end up being OU by usage regardless.
Any remaining games in this round will still allow Mimikyu, including any games that have received extensions. However, following this round, Mimikyu will no longer be allowed in the tour.