Couple notes:
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The Joy-Cons have IR sensors on their rails, and the animation shows them sliding around. It's likely that you'll be able to use them as mice
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There's a new button under the Home button and no one knows what it's for. Every leak showed it had a C on it, but it's deliberately unlabeled here
I don't think Nintendo would put a dedicated social media button on their console after ending support for Twitter, unless they're making their own platform again.