Next year we will most likely see the release of yokai watch 4. 3DS is probably one platform it will release on. Switch then seems like the next most obvious.
But my question is, could we see it on ps4?
A few years back you'd have called me crazy if I said the best platform for dragon quest and monster hunter fans would be the ps4. But now ps4 has dragon quest builders, dragon quest heroes 1&2 and soon to have the superior version of DQ11 exclusively at launch. Even DQX is coming soon. Monster Hunters next mainline entry will be ps4 exclusive in Japan.
So while yokai watch might not seem like an obvious fit for PlayStation it's definitely possible. If you were Sony a few years back looking at the biggest third party games in Japan not on Playstation you'd probably highlight monster hunter, dragon quest and yokai watch. 2/3 are now there so could YW follow suit?
The biggest negative against this is the fact YW probably wouldn't be a good fit for the ps4 audience unlike MH and DQ.