As reported by MacRumors:
“Apple has tested iPad Pros with a Thunderbolt connector that would make them compatible with additional external monitors, hard drives, and peripherals, plus it brings faster data syncing speeds. Apple’s Mac machines have featured Thunderbolt technology for years now, but current iPad Pro and iPad Air models have standard USB-C ports.”
Such an iPad feature has to come with much improved operating system support for external devices, like external monitors, which is currently very limited under iPadOS 14.4. Expect an iPadOS 14.5 surprise support (something along he line of mouse support with iPadOS 13.4 at around the same time last year) or iPad 15 with profound improvements compared to iPadOS 14 which was limited in new features.
Personally, the key for a possible upgrade from my 2018 iPadPro lies in the software, not only the hardware. Also, rumours all points to the 12.9” iPad Pro, what about the 11”? I highly wish that Apple will make the 11”, just a smaller version of the 12.9” version.