Coming in spring 2022 with a full generation leap to back it up. The OG Switch will still be supported for at least it is 7 years old through 1st and 3rd (less demanding) party cross gen releases until it is phased out. This will also be your typical 5 year lifespan for the OG model that Nintendo seems to follow and would not be too far behind the PS5 and NextBox (1.5 years at most).
We may see a NEW Switch type of model that will give a bump in resolution and frame rate in docked mode, but that will be the only notable difference between the two. I do not feel like it will be a X1 to X1X type of difference until the next generation of the Switch line.