Not exactly, the recent updated DK art from the theme park doesn’t make any clear changes to Diddy Kong. I’d use this as the metric for now.
I could see Diddy being a bit further stylized, but probably not to as extreme of a degree. I think the new-old DK and plain old Diddy look fine together.
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As for Smash, I guess that’s the big question right now. Way too early to speculate on, since we only have a couple examples so far, but if this is a really serious movement toward a DK redesign and has been in play for a while I could see Nintendo requesting it carry over.