From Nintendo's standpoint, sticking with the original Switch models for one more Christmas (2023) is basically pure profit especially if they still haven't dropped any MSRPs. Profit they could definitely use heading into a new system launch.
Nintendo's sitting pretty right now, worlds away from how desperate and panicky they were at the end of the GBA's, GameCube's, or Wii U's lives. Those systems died early because Nintendo couldn't wait to start fresh, and I don't think that's the case today.
In a Nintendo system's twilight years, most support dries up but they still try to have one big holiday release every year. I think they'll stretch things out like they've always said they've wanted to do. (I think Iwata at some point said the Wii could be a 10-year system, or am I thinking Kutaragi and the PS3...
) But they've definitely made statements along the lines of "we don't follow the normal console gen timings anymore."