Valve have announced that they will be discontinuing their Steam Link line of hardware once stock runs out, which is already the case in Europe and about to be in the States as well. Of course, existing owners will still get support.
So if you were planning on getting one, you better be living in the States, although it's questionable whether it's wise getting Steam Link now that it's at the end of its life. Granted, Valve have promised ongoing support for Steam Link owners, so it may not be unwise either. After all, the update for streaming came only recently, so we may see a few others before it fizzes out, although we wouldn't really be betting on it.
Judging by the reaction from existing owners, many of whom apparently have a pair of Steam Link devices, it's a sad day indeed. Most of them are aware of the niche nature of the hardware, as well as the fact that it hasn't been as lucrative for Valve as the company would've liked.
Steam Link never reached the heights it was intended to and Valve probably know it better than anyone. The company had quite a few price drops and frequent discounts, even going as low as $2.50 at one point, even though shipping costs meant a jacked up price of $8 or somewhere in the ballpark of the figure.
Although Steam Link's existing customers will continue to receive Valve's support, the company will now be focusing on the software version of Steam Link. The app is available free of charge and also allows you to stream Steam games to phones, tablets and TVs, without using up bandwidth or anything. Naturally, Steam Controller is supported via Bluetooth, as is the case with many other popular Bluetooth peripherals.