A new API spotted by WalkingCat in Windows 10 build 18922 appears to suggest something of the sort. It contains references to pen buttons and a pen dock, while Twitter's Albacore has discovered a new feature with the name PenTailDockEvents.
The references appear to line up somewhat with a Microsoft patent called ‘Base Station for Use with Digital Pens'. In the patent, Microsoft talked about a dock that would store, charge, and sync the settings of a digital pen. You could, for example, place someone else's Pen in a dock, use a form of authentication, and then use it as your own.
These most likely already have a use, there's a new feature called PenTailDockEvents with the ID 20840718
Don't have a pen myself so can't really check though
— Albacore (@thebookisclosed) June 20, 2019
This could be very useful if you have multiple Surface devices or work in a collaborative environment. The dock could also have buttons to perform certain functions, switch between profiles, and more.
As a 18922 build API, it's likely such a device wouldn't come until 2020, at the earliest. However, it's also worth noting that something as vague as code references isn't enough to confirm anything. Microsoft routinely tests devices, and the names could be misleading.
Of course, Microsoft has already released a Surface Dock, but it's not what you'd think. Despite the name, it's essentially an adaptor to plug a laptop into a compatible PC. The tech giant is exactly immune to axing products at the last moment, either, so it'll be interesting to see how the story develops.