Finally! This is the first time for the Pokémon core series. An evolution (mega or regular) that lowers a particular stat. Mega Sableye is confirmed to have higher Defense and Special Attack than Sableye, but slightly lower Speed.

Is /vp/ as hyped as me for this pinnacle of thinking from GF's side?

(I always thought Raichu was slower than Pikachu based on what was said in the anime. Maybe they will alter Raichu's stats? I mean they DID change a lot of older generetion Pokémon stats in the transition to Gen VI. As of now, Pikachu really have no excuse not to evolve, even by holding a Light Ball in battle).