Bloomberg: At least 11 studios are in possession of a 4K Development Kit for the Nintendo Switch.

[Wman1996]

hinch said:

Yeah its pretty obvious a new Switch is in the works.

Going to say they're gearing up for Switch 2 next year (Q4). By which time it will be just over 5 years since the NSW launch, which sounds about right for a Nintendo hardware cycle.

Nintendo has never released a successor to a platform as successful as the Switch less than 6 years before the initial release.

The Game Boy Color took forever. And if you don't even count it as a successor, then the gap between the GB and GBA was even more pronounced. 

The 3DS launched 6 years and a few months after the DS

The Wii U launched 6 years after the Wii.

I know the DS launched not too long after the GBA. But the Switch has outsold the GBA by a notable margin, and the DS was genuinely going to be a third-pillar. But by late 2005 or so, Nintendo saw the writing on the wall. The DS had earned its spot beyond third pillar and as a true successor to the GBA. 

The Switch could have a successor in late 2022, but I don't see it. Q1 2023 seems the earliest, and I find Q4 2023 the most likely of all.