By my calculations, I think Switch just about gets it done assuming a 3DS-style replacement cycle:
FY2023: 141.5m (16m [13.74m (Q1-Q3) + 2.26m (Q4)])
FY2024: 152.0m (10.5m (-35%))
FY2025: 157.5m (5.5m (-48%))
FY2026: 159.5m (2m (-64%))
FINAL : 160.0m (0.5m)
This is assuming September 2024 release date for Switch 2, minor price cuts (lets say OLED gets dropped to $250-300 and base switch is axed), and one more big release (ie pokemon) for switch in 2025
I'd put the likely range at about 150-160m rn, depending on post-replacement support. Worst case, if we see a DS or PS4 style replacement, I'd say we'd be looking at about 148m-150m as a floor, with 165m as a high end assuming worse sales for the Switch 2 and aggressive price cuts for the OG switch