I think the reason it's kind of confusing is that the Vita is so well supported and a lot of the PS4's support has come from leveraging existing Vita games. It could have quite the knock on effect.
I think we need to step back and look at the bigger picture here.
Dedicated devices in Japan are a shrinking and - on the worldwide scale - largely irrelevant market.
The PS4 has moved 1.7 million units in Japan out of 25+ million worldwide. Japanese software marketshare in the West is minuscule.
Sony could never get another Japanese developed game on PlayStation again, and it'd have no meaningful impact on their business.
Sony's behavior reflects this reality too. For all intents and purposes, they're a Western publisher. They're not making new studios in Japan. They're not giving them progressively bigger projects. They're not buying companies like Atlus or From Software when they're up for sale. The few larger investments Sony has been making in Japan (Gran Turismo, Bloodborne, Street Fighter) have been about appealing to a variety of highly dedicated audiences in the West.
Sony also doesn't have to worry about losing audiences for any notable product lines because they don't have any content that appeals to Japan. They're giving up a few games that sell a very modest number of copies, not losing Animal Crossing, Tomodachi Life, and millions of copies of Mario.
No one at Sony is talking about how handhelds are important to them. In fact, they get progressively more dismissive of the system both through statements and actions. They aren't attempting to hype some major comeback or even excite people about the product line in general. Basically the entire focus is on the PS4.
It's a dead product line. There's no incentive for them to continue. It doesn't matter if they lose fifteen Bandai Namco anime tie-ins and a bunch of niche games, because they're completely insignificant. If there's a third party game that's actually relevant in the markets that make up their fundamental business, chances are very high it will show up on their platform regardless, and if it doesn't, it's still not a big deal because they have an endless line-up of Western titles instead.