Wouldn't count on that, sadly. As you said before, the current situation where the PS4 gets defacto Japanese support due to being the only modern platform that is also somewhat viable over there is not something Sony wants to give up. Expect even more moneyhats like these from Sony if the Switch shows signs of becoming a success.
Yeah. I don't expect it. Sony's strategy is to accept that the Japanese market is collapsed and things are a problem for them whenever Nintendo manages to make room over there because when the Japanese market has room to grow that exacerbates the issue that western and Japanese consumers want different sorts of platforms and games and makes it harder for Sony to both put out a western corebox and have Japanese support. If Switch works and with its mixture of specs/portability attracts Sony ecosystem developers to bring PS4 games over, that's letting Nintendo get one foot in the door and pressures Sony to make similar concessions to Japan going forward. Concessions like going hybrid, which annoys western corebox fans. Sony doesn't want to do this. They've accepted what's happened in Japan (thanks in no small part to their own decisions).
It's best for Sony as to Japanese support, which is one of its distinguishing features versus XBox, if the Japanese market remains settled and small. Nintendo has set itself up this past decade that it is best for them to open it up. There's conflict there.
This is the Wii/PS3 conflict continuing, where PS3 trashed a lot of the Japanese scene and Sony is having to live with that, while Nintendo keeps trying (and failing with Wii U) to provide an alternate way forward for Japanese consumers and developers.
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Now I doubt Japanese support is that important to PS success, but it is a tool I'm sure they're glad they have, especially in Europe and Asia.
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All that said, I think people could peacefully coexist. But there's definitely a danger, however remote, however small in Switch to PS and I could see a move on Monster Hunter as a preemptive defense against this.