Done right it can probably remove more money than Sony is comfortable with. They stand to lose a LOT of money if they convince gamers that they really do not need to buy their HW to play games.
PSN+ subscriptions are at risk, MTX and third party royalties are at risk, etc…
They have a very successful moat, they sell consoles (quite a lot compared to MS), they have lots of third party sales and lots of paying subscribers to their services.
They do not have the amount of publisher houses in house like MS now does (and MS's Xbox HW business is nowhere near as healthy), they do not have the kind of mindshare with first party content to live off of that only. I do not believe they have a real shot to get PC players to download their store app and buy first and third party games from them (steaming them away from Steam).
The idea of porting and launching all their games day and date on PC would be suicide for their console business as a whole and would remove a LOT of revenue they currently make. Once the users were to flee, they do not easily come back either so you cannot put the genie easily back into the bottle.