Q1 2024 is in the lead atm but I’m sceptical. That means Nintendo would either announce it just a month or two before release, or announce it in 2023 and risk it affecting holiday sales. True it happened with the Switch but the Wii U was already dead at that point. I’m going with a release either Q4 this year or Q4 next year.
And I don’t give much weight to arguments that Switch 2 will come later because the Switch still sells so well. That never stopped Apple from releasing a new iPhone.