Switch 2 in 2023 would be one of the dumbest things Nintendo could do. The ideal timing for a Switch successor is a launch during the fiscal year where the current Switch platform can be expected to fall below 10m units in shipments and that's not anytime soon.
Regardless of what you think is dumb, they have historically done roughly 6 year windows (sometimes less like Wii U -- Switch, sometimes more). They obviously think its smart. You have to plan out generational leaps years in advance, it can't be a reactive thing, otherwise they will have a bunch of their teams making new engines/games exclusive for Switch 2 and suddenly tell those teams to wait a year or two to release it from when they normally would. Switch had to come early because of Wii U's failures, which is why it was so dependant on Wii U ports early on. Nintendo will want the return on those games as soon as possible and there is no way, 4+ years into Switch's life, that Nintendo isn't working games for their future device. When they started Switch's life they probably mapped out all the games they wanted to make from their teams for this device before moving on to the next device's games.
And Nintendo doesn't want a year where they only sell 10-15m units. That stretches out the lifetime sales of Switch, which seems great to us that care about lifetime numbers, but they are much more concerned with profits each year (not generational profits). If they think they will sell a lot more units by having Switch 2 out then they will absolutely do that. Why sell 10-15 mil Switch 1's in 2023 when they could sell 15-20 mil Switch 2's + 5 mil Switchs (discounted) in 2023?
People always fixate on generational numbers on this website, but that's not how businesses work. Nintendo does't care about last year's financial report, shareholders don't either. It's all about the present year's financial outlook.