I own a Steam Controller, Steam Link, and a Valve Index. They're all excellent devices and I really wish I had purchased a second Steam Controller and Steam Link when they were clearing their inventory. Even after discontinuing the hardware, the devices have continued to function as well as they ever have (actually even better thanks to continued updates).
I'm not surprised Valve has trouble continuing to produce hardware with low sales volumes. That said, they have certainly proven themselves to me with the quality of their devices so this one naturally has my attention. I don't buy products until reviews are out, but this one sounds pretty good on paper. The GPD Win 3, Aya Neo, and One Xplayer have all already proved the concept is viable and I'm excited to see Valve's take on it.
Also, to be fair the whole reason they stopped making Steam Links is because there are many other products out there now which can run the Steam Link software. Their hardware offering simply became redundant. There's no shame in discontinuing a product which no longer makes sense for the overwhelming majority of potential buyers.