Too lazy to pick a pic
Because, like Scraggy, this Riolu is hotheaded and doesn't mind picking fights. It isn't farfetched to expect Ash to let Riolu battle. And while it was Kuk-I mean Masked Royal's(!) idea, Ash was OK with letting Litten battle Incineroar after it rushed down to the arena to ask for a fight. Maybe a similar thing might happen.
Except litten was a fan and have more common sense, while we don't know how fight/see mega lucario will affect riolu, who are very thick headed by now. But, yeah, not thinking riolu will fight here, but I'm sure it and Ash will fight Korrina and lucario eventually. Dunno if before riolu's evolution or not.
Unless Riolu doesn't show up at all is the only way I can see Riolu NOT WANTING to participate.
And if Riolu doesn't show up, I feel like it undermines the entire point of bringing Korrina back.
Look unless this is a PWC match and only if its confirmed will Ash's team against Korrina matter. But I don't think it will be believable AT ALL for Riolu to NOT want to battle Lucario, it's just not realistic given its character.
I just severely doubt Riolu will understand that it shouldn't be battling against Lucario/Korrina and if it this scenario happens, I feel like Riolu would pout or maybe even run away or resent Ash. Unless of course Riolu isn't even with Ash.
Pretty much. There isn't how to know without a summary/longer preview/see the actual episode, but it looks pretty obvious Ash's riolu will be in the episode.
Also, even with the aura synchronization, riolu isn't greninja. Ash-greninja worked because both Ash and greninja were very similar in personality and attitude, despite their differences. By now, it looks like riolu want to be stronger only by itself and the ends justify the means. It will lose if it fights Korrina's lucario, but, I think Ash will take time to properly bond with it after that.