A smaller Switch will still be able to connect to the TV.
A Switch with a bigger screen wouldn't require a new model. Nintendo/3rd parties could make any size portable screen for Switch to slot into.
A new Switch isn't going to run at docked speeds in portable mode. It will all go into battery life.
Nov 2016 - NES outsells PS1 (JP)
Don't Play Stationary 4 ever. Switch!