With Switch being around 20-25% down each following year after 2020, I don't see Nintendo waiting till 2025 to release a successor.
They will announce it probably by the end of this year, and they will release it either holiday this year or spring next year.
Historically, after 1 or 2 years at most after the peak period of a system, Nintendo always releases next system. Now it's gone even further. However it won't be infinite.
I expect Switch to finish at around 135M this year, and with successor on the market next year, I expect Switch to finish 2024 between 142 and 145M at max.
Doing totally Lifetime no more than 150M.
Generally before a console announcement a lot of rumours and leaks happen in the months before. At the moment there has been very little said about a switch successor so I feel like this year is unlikely next year maybe.