Yeah, I was really hoping I would get to the end of Tropical Freeze and find out that Frederik was secretly K. Rool in disguise. It would have been a really epic revival, and even could have included a sequel hook for DKCR3 with K. Rool building a Kremling ermy behind the scenes.
K. Rool is in such a weird situation. His absence from the Returns games seems to indicate that Nintendo doesn't want to use him, but he also made a completely random appearance in Mario Baseball. I don't exactly expect him to show up as character DLC for this, unless he does really really well on the poll, but I feel like he has to show back up in the DK series eventually. And at that point his Smash newcomer trailer is only a matter of time.
The fact he got a DLC costume is pretty significant I'd say. There's only a handful that have been made of actual characters, Nintendo ones at least, and it seems pretty left field of all the characters they make first they make a K.Rool one, especially since he's a western character and has been underutilised in the last decade. His support goes all the way back to Melee - same with Dixie, and his supporters have always been pretty vigilant.
I still think that he has a shot. The Mii outfit doesn't mean much since Samus and a couple of other playable characters have Mii outfits too. The Mii outfit also gives us an idea of what he would actually look like in Smash 4's style...heck, maybe a model's already been worked on and they used that to translate into his Mii outfit to test the waters or something.
But it's annoying how much Nintendo's Japanese studios and developers kinda turn their nose up at western character designs and concepts, even though largely they are quite ugly or don't compare to the Japanese style in their execution, but Rare characters like Dixie and K.Rool are still quite memorable. They're not overdesigned - and over the years when other teams have took over managing them they've redesigned them slightly anyway to better merge with their other properties.
I do think that the DKC country games while unique at the time do look terrible, especially nowadays. They aren't as timeless in artstyle as you see in games like Yoshi's Island or Mario World, and in the same vein, seeing Killer Instinct next to Street Fighter II, but they were still experimenting with things the guys overseas were too reluctant to try.
I kinda went off on a tangent there, but I do hold a special place in my heart for Rare's characters that were left in custody of Nintendo like Dixie, K.Rool, Krystal et cetera. There's lots of support for them here and consistently has been, and whenever we see poll results it seems Japanese fans are the same!
I think it might just be Nintendo themselves steering clear of any Rareware association altogether after the split, but since Retro are a western studio you'd imagine they'd be less inclined to ignore Rare's input to the franchise and listen to fans (which they did - revisiting the music in TF) but I guess they just wanted to try something fresh and have their own chance to contribute to the universe, which is fair enough really. Would definitely be nice to see K.Rool in a third game by them though since I'm sure he's itching for revenge on the Kongs by now.