There is nothing to say that Ash can’t get more then one Mega Stone. Yes, Ash has a strong bond with Charizard however unlike Charizard Lucario is a current member of the current team, and given that it looks up to Korrina’s Lucario it’s pretty likely that if Ash uses Mega Evolution that Lucario will be the first one to Mega Evolve.
Really once Ash has a keystone he will just need the Pokémon respective Mega Stone and a strong bond with the Pokémon and it will be able to Mega Evolving.
Basically Ash’s Lucario will likely be the one to open the door to Ash using Mega Evolution paving the way for some of Ash’s other Pokémon to possibly use Mega Evolution at a later point as well.
I fixed it for you. I took active out, since it hasn't done anything, nor has it appeared on screen since the last Unova episode.