Is the PS5 going to have the same type of support the PS4 has, or are some of those devs going to convert to the Switch, since it's the only system selling currently in their home country? This is something that hadn't occurred to me until reading this post. I would like to think that the sales the Japanese devs get from selling their games overseas is enough to have faith in the PS5, but I wouldn't be surprised if things start to change.

This is more of a hardware issue than anything else. Sony needs to deliver the right hardware for the Japanese market. If they deliver the right device, they can greatly enhance the Ecosystem, not only in Japan, but around the world. They have the tech to deliver a PS Phone that would be capable of running downscaled PS5 games, utilizing the same development tools, it is just a matter of them doing it. If Sony killed off the Xperia Brand, and brought all of their Sony Mobile Patents, and Employees under SIE, they could do some incredible numbers in Japan. That would assure them continued support from their 3rd party parteners. 

If Sony makes the right moves going forward, they will be able to recapture the Mobile/Portable market they have lost. Adding a dedicated 1st party JRPG studio (not buying, but creating), would also help things along. It's just a matter of better allocation of manpower and resources. People always say Sony can't support Mobile, but that is bogus. We have reached a point where the line between home and Mobile has shrunk dramatically. This is not the days when Home consoles where running games at 540p/20fps, with no room to scale down for Mobile. PS5 will more than likely be a 4K/60 machine, scaling down to 720p/30 for Mobile is a cake walk. Same architecture, same tools. Nothing like when they had two seperate platforms such as PS3/PSP, where they had to develop for completely different architectures, with different tools, and basically make a completely different game for the Portable. 

The fate of Sony's 3rd party development support from Japan Studios, rest completely in their hands. Do it right, and they will continue to fly high. Fail to expand the ecosystem, take advantage of new technologies, and deliver the on current industry standards, and they will loose that support to Switch and other platforms. 

No, they dont need them I suppose. Especially when you consider 3rd party studios can fill gaps with exclusives as well.

No i think they should invest in a better server infrastructure like microsoft did years ago, ccp is future and ms is 10 years in front of sony in this buisnes.

Yep, that have truly show on X1X winning the gen.

No need for it really.

You can never have too many.... unless you cant finance them, or it starts cutting into the budgets you can give them.

Yes PS4 has tons of games you cant play on a xbox, and thats a huge advantage for them.
its why its selling so well, people dont want to miss out.

Agree OP, they dont need more studios. They should just focus on expanding their studios (which they are), and building more relationships with third parties. They are well set for next gen.

Although at the same time, they've closed two studios this gen, too.

And the closed studios were bigger than the ones that were opened,  which were an indie tier studio and a VR studio.

All of those PSVita devs are more likely to make games for Switch or both Switch and PS4.  Given the portable nature of the Switch and how the Japanese market is, the PS4/5 will never get the same support the VITA did while another portable option is available.  Sooner rather than later, 3rd party Japanese support will hit both systems at best, outside of the most visually demanding games (which also go to XBox).

No. Sony doesn't need more Studios. Just like you don't need to play video games.