Best answer: No. The standard 16GB NVIDIA Shield TV has not been discontinued, nor has any other NVIDIA Shield TV model.
Amazon: NVIDIA Shield TV ($178)
Despite rumors, NVIDIA Shield TV has not been discontinued
Due to a lack of stock in late 2017, as well as multiple GeForce forums posts, it was believed that NVIDIA first discontinued the basic 16GB Shield, but then changed its mind and discontinued the Shield TV Pro.
While there may have been plans to discontinue the Pro (many users just connect their own NAS for storage anyway), and it may have even been out of production briefly, you can still very much buy the Pro and three other NVIDIA Shield TV models right on NVIDIA's website, as well as from Best Buy and Amazon.
There are two NVIDIA Shield TV models to choose from
Not only is the NVIDIA Shield TV not discontinued, but you have three other configurations to choose from, depending on how you want to use it.
NVIDIA Shield TV
This is the basic Shield TV. It features 16GB of onboard storage, 4K HDR support, built-in Google Assistant, as well as all that streaming and live TV goodness.
NVIDIA Shield TV Gaming Edition
This iteration has 16GB of onboard storage and comes with a rumble feedback gaming controller, as well as access to the GeForce NOW beta, which is NVIDIA's way of syncing gaming across Mac, PC, and your Shield TV. (Yeah, Mac gamers can play on Mac without Bootcamp!)
NVIDIA Shield TV Smart Home Edition
This has 16GB of onboard storage, all the goodies of the original, plus it comes with a SmartThings hub and a SmartThings Link, which transform your Shield TV into a Zigbee and Z-wave smart home hub. If you're looking to build a smart home around your TV or you simply want an excellent hub, this is your buy.
NVIDIA Shield TV Pro
Despite much speculation, this version is still alive and kicking. It has all of the capabilities of the other iterations, but it has 500GB of onboard storage and the Plex Media Server built in.
NVIDIA Shield TV
Sometimes basic is the absolute best.
The OG NVIDIA Shield TV is the way to go if you're just getting into things. You can just buy the gaming controller on its own or even go for third-party options. There are also many ways to build a smart home, but to enjoy all that the NVIDIA Shield TV has to offer, the basic option is more than enough.