See this thread from ResetEra for more details.

From a Nintendo Dream interview (translated via machine translation by Famiboard user TheDinoman)—

Tanabe: “It's been 40 years since I joined Nintendo. This Metroid Prime 4 will be the last game I work on at Nintendo. However, we didn't deliberately do anything "special." Instead, like with previous Nintendo games, we worked together with Retro Studios to complete it, hoping to provide a fun and unique experience for players of all ages and types.I would be very happy if this game leaves a lasting impression on those who play it. And for those who haven't played it yet, I hope you will experience the unknown planet of Viewros through Samus's eyes.”

Now, it should be noted that it is still entirely possible this is merely a “Pikmin 4 is in it’s final stage of development” mistranslation; however, the contents of the paragraph do appear to corroborate that this is the intended message. Sad to see him go. :(

Further info: Here is a link to Tanabe’s Wikipedia page, which lists all his works and roles during his time at Nintendo. Looks like Paper Mario will be led by an entirely new face… that’ll be exciting at the very least!

Long and great career. Retire happy Tanabe and enjoy! Thank you for many great games!

He contributed to a ton of great games, hope he enjoys his retirement, he's certainly earned it.

Goodbye, Tanabe-San, and good luck. 😢

Thank you for all of your hard work, Tanabe-san. Enjoy your retirement.

Seems like the next few years, we might see a couple of these high Nintendo figures of yore taking their leave one by one ...

Hopefully they chaperoned excellent brilliant minds at the heads of these teams !

When you think about 40 years working at the same company is hugely impressive.
Congrats to Tanabe on his long career 🥳

Most of the old guard of Nintendo is aging out of the company. Will be interesting to see where the Metroid franchise goes now.

Yeah just today news broke that Hideki Konno is also leaving; he was the producer of much of the Mario Kart series, and directed Luigi's Mansion:

https://nintendoeverything.com/hideki-konno-nintendo-retirement/

Guys like Miyamoto and Aonuma are also getting really old now and will likely retire soon

Miyamoto is basically semi-retired at this point, he's basically just overseeing the movies and theme park expansions, likely he sees that as his duty to get right as it's going to be a fundamental pillar of Nintendo's future (ie: getting the live action Zelda movie right, Mario movie was already made to his liking and was a giant blockbuster).