Well, besides the fact that Nintendo has a history of trying completely new things, it also sticks with what it has. Especially in the field of mobile devices.
For example, look at the Game Boy series. There have been several generations of Game Boy. Think of the original Game Boy game, Game Boy Color Game Boy Advance.
In total, this series (which was all backwards compatible) ran from 1989 to 2010.
With the successor, the DS is a similar story. The DS was introduced in 2004, and eventually lasted until 2014 with the DS, DS Lite, DSi, and DSi XL. However, its successor, the 3DS, can also play DS games. The 3DS and variants ran from 2011 to 2020. A total of about 16 years.
Wii, including the Wii U, lasted from 2006 to 2017, with the Wii U unfortunately failing. However, that support is still worth 11 years.
There are more examples, but it also happens that if something sells well, Nintendo will continue to do so for several generations. Given the current success of the switch, it seems to me that it is 100% reasonable that we will have a switch of 2 that is compatible with the current platform. When is that? That could be in 2022 but also in 2023.
Even then, you don’t have to expect a 4K version. I think you should be happy that you can play handheld 1080p and that it will dock at 1080p at 60fps. And we’re not talking about titles developed for the new generation, but more about existing games that will work best.
It’s hard to say what the new titles will do.