I see no reason to abandon the hybrid form factor for a tiered one.
Modern APU's are able to scale well with different power profiles. If Nintendo wants the docked experience to be greatly superior to the portable experience, then it is just a matter of having decent cooling, and allowing the platform to scale up to 25W - 30W when docked.
We already see how well the Steam Deck (and newer PC portables) scale with different power profiles.
My guess is that Switch 2 will probably use a mobile Ampere-based chip (if Nintendo goes Nvidia.) That'd probably put it between an RTX 3050 mobile and base Tegra Orin when docked, and akin to the RTX 2050 Mobile when portable.
That'd be decent for a 1080p/1440p target resolution aided by DLSS. It'd be a generational improvement over the Switch, which is all Nintendo needs for people to want it and its games.