Current sales suggest that Switch outsells 2019 numbers next year, especially until the launch of Switch Lite back in 2019. So 2024 should be the first year in which we meet 2017/18/early19 numbers again with a weekly base below 200k. That still would be pretty good for such an old system.
The upcoming games lineup for 2023 suggests full first party support for next year. No signs for a need of any successor yet.
Switch performs better than I would have ever thought. It should reach 150M without any problems with a good chance becoming the most successful video game system of all time.