If Sony wants to reverse this trend and really be competitive against Nintendo in Japan, it has to start in house. They can’t just rely on throwing huge money on exclusive deals forever, timed or not. Square Enix, Capcom, Sega/Atlus, and all the other Japanese 3rd parties may have other plans. And while I’m sure they’ll continue to develop their games for PlayStation, they can’t just ignore Nintendo and the Switch forever. More specifically, they can’t keep looking for excuses to justify to their investors why they are continuing to ignore such a profitable platform that has proven to he a grand slam not just in Japan, but worldwide as well. Investors will see that as leaving money on the table, which it is, and start to lose faith.
Sooner or later, mainline entries for all those franchises that have been almost exclusively PlayStation for a while such as Final Fantasy, Kingdom Hearts, and more recently, Persona, are going to come to the Switch as well. And if this downward trend continues when that happens, it’s going to look even more bleak for PlayStation in Japan, and it may even start to have some trickle effects worldwide. For example: If a sizable, considerable chunk of the Japanese audience chooses the NS/NS2 version of Persona 6, Next Gen Monater Hunter, or Final Fantasy XVI, over the PS5 version, who’s to say the same won’t hold true for the Western audience? So those are lost hardware sales, lost revenue, and lost profits, right out of Sony’s pockets that are going straight into Nintendo’s.
If they don’t want that to happen, which I’m sure they don’t. They have to take matters into their own hands and start to seriously develop, appeal, cater, and market with the Japanese audience in mind. Ghosts of Tsushima is a step in the right direction. They need more of that, much more.
Sony certainly doesn't want it to happen, but it shouldn't be expected that they'll take actions beyond moneyhatting Japanese third parties, because Sony's history in the console market is one of flight, not fight. When the odds are stacked against them, Sony will move elsewhere instead of standing their ground. You can see this in PS3 vs. PS4 sales in Japan and also the handheld console market as a whole. Based on how the PS5 is designed, there's no good reason to believe that Sony will take a stand in Japan.
Ghost of Tsushima's success is circumstantial rather than deliberate. I doubt that Sony ordered Sucker Punch to make a samurai game, rather Sucker Punch decided to make a samurai game and that happened to be good to market in Japan.