Bluntly, if Nintendo was embracing a considerably larger design, they wouldn't be working with a 9W GPU in T239.
T239 is impressive, yes, but at 4nm, it consumes only as much power, and produces only as much heat, as the original Nintendo Switch, while being PHYSICALLY SMALLER than the original Tegra X1 and the shrunken Tegra X1+.
So unless they've ever gone outside the design parameters of T239, or switched to a different SOC entirely, NG Switch isn't going to be some Lovecraftian horror of a brick, it's going to be just as slim as the Nintendo Switch, or they could even make it thinner, just inevitably larger in width and height thanks to a bigger screen, and likely this allows for a bigger battery, too, but they won't sacrifice portability to do that.
A thin device with chuuunnnky controllers is both portable and comfortable, and it appears T239 is perfectly positioned to deliver a device both thin and powerful.