There's no NEED to include anyone.
K. Rool SHOULD be included in this game.
But the final decision is Sakurai's.
And if K. Rool doesn't make it, it ain't the Chorus Kids' fault.
There is a valid argument in favor of a new DK rep, though, that far outweighs the argument about Rhythm Heaven being a fairly new franchise with decent sales.
http://www.vgchartz.com/game/47661/rhythm-heaven/
http://www.vgchartz.com/game/45674/donkey-kong-country-returns/
6m copies sold worldwide of DKCR.
6 MILLION. So, yeah, that's two years older than Rhythm Heaven.
http://www.vgchartz.com/game/73169/donkey-kong-country-tropical-freeze/
Six months. 570k in six months, compared to 870k for Rhythm Heaven Fever in 2 years. And on a console with a far, far weaker install base.
Now, I'm not arguing against Rhythm Heaven or anything. But also compare it to Kid Icarus: Uprising and Fire Emblem: Awakening.
http://www.vgchartz.com/game/70704/fire-emblem-awakening/
http://www.vgchartz.com/game/45683/kid-icarus-uprising/
With these sales numbers and DK's long history, DK should honestly have two new reps in this game.
Yes, its VGChartz, the sale numbers will always be a bit off. But comparing the sales, its clear who the winner is here.
K. Rool himself may not NEED to be in the game, but compared to other franchises expected to get additional playable reps, DK NEEDS at least a third rep, if not a fourth, just based on the sales alone.
Now, I'm not knocking on a new franchise rep getting represented. New franchises are always great, the bigger annoyance is the idea that Fire Emblem gets a third rep over DK, when the DK franchise sells far more (as much as I LOVE Fire Emblem, too). And compared to Kid Icarus and Fire Emblem's "revival" (technically FE was never dead, it just got lackluster sales) DK's revival was far bigger, and Tropical Freeze is selling quite well, too, especially for a Wii U game.