Speaking of Slaking, I'd really like to see a mega-evolution for it. Think it really deserves one, honestly. It's such an underrated Pokémon; if it does wind up getting a mega, it could hopefully gain some boost in popularity. If they do decide to give it a mega-evolution form, I'd like them to take away its Truant ability, as it's one of the things that's held it back all these years, haha.
I think a Mega Slaking would still be quite overpowered due to Slaking's already godly stats. It'd probably end up in Ubers before one could even blink. There's a reason Slaking has Truant, it's to avoid being too overpowered.