I have to agree that the source of this makes it dubious. Still it is fun to speculate. And who knows, maybe Goodereader actually got it right for once.
I googled for a Paperwhite 4 but that's the only current web page that mentions it. Some older pages ask if there'll be a Paperwhite 4.
As for the light, I don't miss the color change on my Kindles. On my Nook Glowlight 3 I did play with it and I found adding just a little warmth to the light was kind of nice. Nothing automatic. I just warmed up the white light and left it there and I like it. But I read more on my Kindles which don't have that and I don't miss it.
I just got a new Paperwhite in their last sale. I have a couple of old ones as well as a Voyage. I start getting nervous when my ereaders get older because if I end up in a nursing home I want it to be fresh and last a long time. I'm in a retirement home now living on social security which I manage myself. In the assisted living and nursing homes they get your social security and give a small allowance which isn't enough for an ereader. I'm pretty healthy at the moment but at 77 that has to be part of my planning.
Barry