Any time between November 2024 - March 2025 would be fine, imo.
The important thing is that they announce and moderately tease it in 2024.
I wouldn't mind something similar to what the Switch had. October announcement/teaser, January showcase, March release.
That puts the Switch 2 and Switch 8 years apart, which I expect will be typical for a console generation these next few decades.
Second half of 2025 would probably be too late though.