I think the best way to think about it, given what we know currently, is that Switch 2 (when docked) is probably going to be anywhere between the original Rog Ally Z1 (non-extreme) (if on 8nm node) to maybe slightly better than an RTX 3050 Laptop 35W (if on 4nm node) in terms of performance.
That puts it about a half GPU-tier to quarter GPU-tier below the Series S.
The Rog Ally plays games at similar graphics settings and framerates as the Series S with about 50-70% the internal resolution of the Series S. An RTX 3050 Laptop 35W does similar at about 70-80% the internal resolution of the Series S.
That's what we should probably expected for a docked Switch 2.
In handheld mode, I'd expect Steam Deck OLED 12W level of performance, assuming it is on the 4nm node, moderately less performant if on 8nm.
In 2025, when the platform releases, this would be a mid-range gaming handheld. By then the top-range handhelds will match and maybe even exceed Series S performance levels, having the Z2E from AMD or possibly Lunar Lake chipsets now that Intel is competitive. These will cost $600+.