Source: WinFuture
A recent FCC listing all but confirms that the S Pen is coming to the Samsung Galaxy S21series—the Galaxy S21 Ultra in particular. A test report for model number SMG998B explicitly stated that the Equipment Under Test (EUT) device is usable with an S Pen in hover and click modes. The report said, "The EUT can also used [SIC] with a stylus device (S Pen). The EUT operates with the S Pen in two different inductive coupling modes of S Pen motion detection (Hover and Click) operating in the range of 0.53 –0.6MHz."
The listing also mentions wireless power transfer, allowing it to charge things like the rumoured Galaxy Buds Pro; and support for Wi-Fi 6E and UWB. According to Samsung Mobile President TM Roh, the company plans to utilize ultra-wideband more in 2021 with partners' assistance, including using UWB to locate objects or pets, open doors, or personalize car experiences. We should hear more about the Galaxy S21 series in January. The rumoured launch is on January 14, 2021.
Source: The Verge