Oh, how the mighty have FALLEN, though! I mean, honestly. Nobody gives three cruds about Mega Blaziken now. (Though... I'm willing to bet that GameFreak saw this coming and actually made another Mega for him.)
The only way I'd end up dropping Sableye for my Alpha Sapphire run now would be if... heck, it won't be happening. The only way I'd be dropping Mega Sableye would be if Hydreigon or Honchkrow gained Mega Evolutions. They're the only non-Legendary Dark-types that I like better than Sableye.
Not only do I like the design, but I've been pleasantly surprised by its new dimensions in competitive play. I actually think that he has the potential to become a monster with his new Ability, given the right stat distribution. Even if he sucked, I'd find SOME way to use him. He's one of my favorite Dark types and possibly my favorite Ghost type; also, regardless of how his Mega goes down, his regular form is still viable.