ZigBee is already so widespread that I don’t see it going away. I’d be much more worried about your WiFi devices.

While WiFi as a network technology certainly isn’t going anywhere, most WiFi-connected devices talk to a service on the internet. You probably created an account somewhere to manage your WiFi devices. So if the manufacturer shuts down their service, which happens all the time when they either shut down the whole business or abandon a product line, you will have no way to manage your devices.

ZigBee will continue working as long as your hardware does, because you control the software managing it.

There’s not much point in optimizing completely for price per inch, but when I bought my TV in 2013 I plotted this, and discovered a pretty sharp hockey stick in the graph at 70" and above. So I got a 65" TV. If my graph had looked pretty straight like yours I’d probably just get the biggest that is practical for the space.

Mine supports none, so I also don’t have to worry about it.

The A in ADSL literally stands for “asymmetric”. If you want matching upload you’d use SDSL. But generally you don’t want that, because it sacrifices some download speed.