Might keep the old one S somewhere with a stash of other games on it for copying, really not going to be the fastest transfer that way but hey it's another Tb of storage and media player somewhere.Yep, you can do a network transfer across any consoles on your lan, may not be the most efficient if consoles are wireless though.
Can still pre-order at Microsoft store
The Seagate Storage Expansion Card for Xbox Series X delivers an additional 1 TB of external memory while maintaining the same peak speed and performance as the console’s internal SSD.www.microsoft.com
A short video that shows some speed tests
Xbox Series X storage test: Xbox SSD vs. USB HDD vs. USB SSD vs. USB NVME - YouTube