I think by now it should be clear that 2023 won't be it.
Late 2024 makes the most sense to me. Nintendo needs to find the right balance: They shouldn't kill the Switch off prematurely like they did with the GBA, DS and Wii. But they shouldn't wait too long either because that would mean they are leaving money on the table. Right now the Switch is still on fire. The OP makes it seem like there needs to be a successor soon, but we should keep in mind that the PS4's best (calendar) year according to VGChartz was 19.7 million units. Even if Nintendo misses its current forecast by a bit, that would still put Switch sales above PS4's best calendar year ever. Did the PS4 need to be replaced in 2016/17? Of course not.
The big question is: What else has Nintendo planned for the console? Do they plan on releasing a mid-gen upgrade like GBC, DSi and New 3DS? If so, there'll be plenty of time left for the console. They can also cut the price, but that wouldn't have such a longterm effect on sales. But with the current chip shortage, the pandemic still not quite over and other events it might be hard to release a New 3DS-like new model of the Switch and produce it in large enough quantities.
Anyways, 2024 seems like the most logical choice for me right now, but I wouldn't rule out a 2025 launch.
