I don't get or know what metric you use to measure something like that being "sustainable". And I feel its one of those weird narratives that sensationalism aside, falls apart under a little more scrutiny.
As far as games go, sustainability simply means that the studio/publisher recoups whatever they spent on the development of the game over however many years it was developed for, and makes a decent profit on top of it.
As far as platforms go, sustainability means that over the course of a generation, the platform holder has enough of those flag pole AAA exclusive titles (first party or third party) driving platform adoption and adding pedigree to your library.
And is Sony failing in either of those regards? I would say the answer is a resounding NO.
And no on this AAA thing, this is not just a Sony issue, its an industry-wide issue. Games simply take a much much much longer time to make now. And this didn't just start now. Back in the PS1/PS2 gen, most studios could knock a game out in under 2 years. In the PS360 gen, it was still taking 2-3 years, but that same body of work had become significantly more expensive. Development costs went up almost 6-10 fold compared to the PS1/PS2 gen before it. The PS4XB1 gen, dev times creepd up to 4+ years and became even more expensive. This brings us to where we are at now, with most studios (unless you are over 500 people big) becoming a one-game-a-generation studio.
This is not a sony thing, the alternative is to make smaller, AA titles, but if sony, a platform holder, does that, then who makes the AAA big budget $200M+ games? Take 2? We are simply in a time when a AAA game take such and such amount of time to make, and sony has been very smart with how they have gone about addressing that market, Leveraging both their first and third party resopurces. And I would rather have 1 or 2 such games every year, then have 10 smaller AA titles each year. There are devs for that, let sony focus on the AAA games. Even if the current climate means they come once a year or so. Or as a first or third party exclusive.