It will sell well to all those people like me that have realised that "gaming caves" - when you have a family - are a fallacy.
You can either use them and alienate your family, share it and it just becomes a kids' second lounge with the problems of the first lounge transposed, or it just becomes a room with lots of great kit you never use because when you can use it, the lounge is free also.
The WiiU tablet controller for offscreen play was a win for some of us, because it enabled us to play in the lounge in the company of family without having to commandeer TVs/audio/consoles for hours and hours that other could or would use. I've tried using my phone or PC for remoteplay with Death Stranding and Ghosts of Tsushima in recent years and it just isn't practical as
Giallo Corsa
explained above.
In Japan, where home consoles are in heavy decline I suspect if Sony decide to pack-in this controller for a new PS5 slim model around $550 price it will likely do well and massively increase home console sales in Japan, giving it a good opportunity to do well across the world.