Call me Mr. Negative, but I don't want this Mega Lucario episode to happen. At least, not under these circumstances. I don't like when characters are given things without earning them through hard work. Korrina just giving Ash a Keystone and pointing him in the direction of an island apparently known for Mega Stones is not earning it. Even with Z-Moves, which were just given to him by Tapu Koko, he still needed to go through the Island Trials to use Z-Moves without shattering his own crystals. That worked fine. This doesn't.
And before anyone says it, Ash has earned his right to a Keystone and Mega Stone several times over. But only in the general sense that Ash has been through and achieved a lot without asking for anything in return. It doesn't work once you start looking at it more focused. For this to work, the Keystone and Lucarionite should get 3-5 episodes worth of story around them. With Ash working hard to try and find the Keystone, Goh and Korrina supporting Ash, with an antagonistic rival-type character competing with Ash to get to the Lucarionite first. That way, when Ash finally gets the Lucarionite and can Mega Evolve his Lucario, it is going to feel like he worked his rear off to make it happen.
But that's not what we're getting. So can we just get another natural disaster that makes Japan say "putting this on TV now will be in bad taste. Let's put it off until it becomes irrelevant and gets cycled out of continuity"? Please?