The only thing that annoys me about mega evolution is that I see Game Freak copping out of giving older Pokemon legitimate evolutions to help improve them base wise before making them mega evolve.
I'm happy Sableyes got a mega but I prefer if it have gotten a pre evolution and a regular evolution before getting a mega.
I feel the same way about other Pokemon like Dunsparce, Far'fecth, Zangoose, Seviper, Hawlucha, and others that I can't think of.
With that said, I would love a Weavile mega with Adaptability as it's ability!