BOTW has a sequel coming out which will boost the OG title legs even more. And Zelda games tend to be different experiences between titles unlike the repetitive nature of Pokémon games.

So people who got in with the sequel will undoubtedly go back and buy the original game.

It's going to be close. Zelda has amazing legs, but Pokemon is going to keep selling for a while too. In the end I have to give it to Zelda though. I expect the next Pokemon game to be better while the next Zelda game will be worse. Just my hunch. But if that's true the next Pokemon game will seriously cut into the legs of Sword/Shield while BotW's legs will keep going.

BotW going to sell 30mil. It’s no contest, Pokémon will do 23mil-25mil lifetime but Zelda is selling 4mil yearly and BotW2 won’t cut off BotW legs at all

Then there is the fact that BotW is most likely to get the budget Nintendo select deal in 2/3years