I like the idea of the off-screen dancing because I think it's building up to a hint in the Gym battle, with Ash remembering it (flashback incoming) and also him remembering the words, "Don't give up till it's over!" which will help him win. So yes, I think it will be mentioned in the battle.
Also, a BEACH EPISODE! Although it's apparently centred around Bonnie, it will almost definitely have Serena in a swimsuit, so we'll be able to see Ash' response to that. And it is said to have a Lapras, so maybe we can see Ash mention a Lapras from his earlier adventures.
And like Sheepy Lamby said, XY050 will have Fennekin and Pancham dancing. This will be another Serena-centric episode, so most likely we'll get more hints. This ship is nowhere near going downhill, it's only just powering up!
And about the dedication day towards Amourshipping, I don't really think it's necessary. Every other ship has one, sure, but that's my point. Since Amour is different to those ships (I don't need to explain why) it doesn't need a day allocated to it to gain more appreciation, like the other's did. I'm pretty sure every Pokemon fan would notice Amourshipping, and Serena's crush, so really every day an episode airs Amour is noticed and appreciated. But... if there was a day to commemorate this momentous shipping, I would agree with everyone else: Valentine's Day (Amour=love, Kalos is based off France), or November 21 (airing of XY007).
EDIT: One more thing, I've been thinking about the capture of Pancham (no need for spoiler tags anymore TBH) and I think it's possible for it to be a boy, wearing Serena's (game counterpart) sunglasses. It would be awesome to see Serena take them and wear them herself once, just as a neat little reference. Plus if Ash or one of the others says: "They really suit you!"
And like chicorita3 said, it would be nice to see Pancham trying to win Fennekin's love if it's a boy, we might see a fight between it and Froakie. Might involve Ash and Serena then