While I believe that Pikachu isn't going anywhere, and yes, it is the most recognizable Pokemon of them all, I also believe just as much that if they wanted, they could make some other Pokemon like Eevee, or Clefairy worldwide popular, and recognizable too.
People who are in charge of Pokemon would just need to promote them more through anime, or some other way, and they would need time.
Fans, anime viewers, players, and social media would do the rest.
Just remember how fast Pokemon Go became popular when it came out, or how super popular is Raiden Shogun from Genshin Impact, etc...
People in general usually care about the things that are currently trending.