The main point of first party games should be sell consoles to make the platform profitable from third party royalties. They think this strategy will not affect PS sales and PSN sales. You probably think so too. I'm betting in 6 years from now PS6 will project less sales than PS3 did.
In
this previous post you can see that their hardware, software, game sub and accesories revenue kept growing every year in FY21->FY22->FY23->FY24, with hardware having a small decline in FY24 because the console passed its yearly units sales peak of the generation (passed this point hardware sales keep decreasing, while software continues selling longer).
I think PC+mobile+movie/tv show/other adaptations will help them to continue growing their console audience during PS6, specially in territories that previously weren't important for consoles like non-Japan Asia, MENA or Latin America.
Main reason being that Sony will have a bigger presence in PC and mobile, markets more popular there, plus extra popularity from movies and tv shows, and on top of that Xbox would have lost basically all their market share, while Nintendo will have starting to get some pressure from handheld PCs.
If Sony is smart, they will return to exclusivity again.
With Xbox gone, it'll be much more important.
The opposite. In the home consoles market they defeated Nintendo last gen and MS this gen. After having conquered home consoles, now they are going for PC, where with a few games they already are one of the top 10 publishers of Steam history.
Releasing several games more on PC, and in the future their own PC PSN store, they will be the first serious contender for Steam. Pretty likely they'll use this store to join the PC handhelds market (even if with their own closed OS) that they'll also use to fight again Nintendo in the portables market.
Pretty likely once the cloud gaming tech improved more in mobile and once regulators allow them to have their own store in Android and iOS, they'll also slowly start expanding in mobile.
This expansion is needed by Sony not only to continue growing in all fronts, but particularly to fund their first party AAA games, that each generation keep getting more expensive and take longer to make, which means they need to sell them in more platforms to keep them profitable, and at the same time need to increase the amount of games under development to keep a similar output pace.