According to an interview from Pokemon.com, this month's release of Pokemon Let's Go: Pikachu and Eevee will be the final time Junichi Masuda directs games in the core Pokemon series.
Masuda, who's been directing Pokemon games since Pokemon Ruby and Sapphire (and who did sound design on the original Pokemon Red and Blue) states in the interview that "it's important to have the younger generation at Game Freak take over the development of Pokemon as a series," seeming to indicate he'll be staying at the company.
Masuda returned as game director for the Let's Go games after spending time working on the global hit Pokemon Go.
In the interview, he states that he chose to work on the Let's Go titles because he "wanted to realize that goal by creating games that could connect with Pokemon Go and feel somewhat similar to it without feeling like we were copying it."
For developers who are curious about the careful choices that define Pokemon's game development, it may be worth reading the full interview over at the Pokemon website. Masuda's joined by his collaborator Kensaku Nabana for a conversation that highlights some of the specific choices that have helped the Pokemon series evolve over the last two decades.