A recent Bloomberg report stated that Nintendo was working on a 4K-capable Switch. Nintendo took to Twitter to deny the existence of any such console. It reiterated that only the Nintendo Switch OLED would be launching this year (2021) on October 7.
https://www.notebookcheck.net/Nintendo-shuts-down-rumours-about-a-4K-Switch-being-launched-later-this-year.567629.0.html