According to dataminer SciresM, the recent firmware to the Nintendo Switch references the new hardware with the codename “Aula”.
Aula reportedly uses a Mariko (Tegra X1+) SoC, the same chip currently in the Switch lite and the revised Nintendo Switch. SciresM suggests the chip will be geared to higher clock speeds and that the firmware also references support for a Realtek chip known as “4K UHD multimedia SoC”.
The Switch Pro is speculated to have an OLED screen. SciresM thinks the Switch itself won’t have a higher resolution, but speculates the 4K Realtek chip will be in the Dock to allow a 4K display when playing on the TV.
In addition, the firmware supposedly suggests “substantially” better cooling and battery life for Aula.