to what extent it affects those who already buy the chromecast ultra with the stadia package, because then the promise of not renewing hardware ... is not very true
You don't need to upgrade your chromecast because it's new. The new one most likely has a ui for TV watchers. Stadia still will work the same no matter what device you get. I would say that in the future when they start streaming 120fps than your gonna need to update your "source" connection and compatible TV to hdmi 2.1. Same as people going to get a ps5 or series x this year. But again, that's still considered optional.
One big thing people forget to mention is that the new chromecast box COULD come with the new wifi 6 standard. This really is a big deal considering most people likely don't use an ethernet port.
My Surface 7 Pro tablet reaches 5ghz all over the house perfect (3000 sqft house) and reaches up to 600 mbps with low ping while my other devices cannot.
Wow I never thought on the Wifi 6 thing... That would be realy awesome for a lot of people...
But still most people would have to upgrade their routers If they want to benefit from it.
But I love Nvidia Shield for that very exact reason -> It's a Chromecast mixed with Android TV so I got a seperate remote control and don't have to use a second device, but I can if I want.
I would definitely upgrade to the new chromecast in my living room and keep Shield for the Bedroom because of their clould solution...