Sony Interactive Entertainment Japan Studio, the creators of the Knack series, is one busy studio, as they just released the critically acclaimed Astro Bot Rescue Mission and recently helped FromSoftware produce their PlayStation exclusives Déraciné and Bloodborne, not to mention their valid contributions to Bluepoint Games' Shadow of the Colossus remake and genDESIGN's long-delayed The Last Guardian.
According to Producer Teruyuki Toriyama (Bloodborne, Soul Sacrifice: Delta), SIE Japan Studio's next big thing will be officially revealed at some point next year. His interview with 4Gamer has been translated from Japanese by Twinfinite and Editor Giuseppe Nelva has noted that the term "taitoru” could mean both one title or multiple titles, but the given context seems to point to only one unannounced project.
Considering that FromSoftware President Hidetaka Miyazaki recently confirmed that the studio is working on two all-new games that haven't been revealed yet, there's a chance that SIE Japan Studio is helping develop their projects once again, as Toriyama-san produced From's PS4 exclusives Bloodborne and VR experience Déraciné, and there's no doubt that a Bloodborne 2 would make a lot of fans happy.
Of course, another possibility is that SIE Japan Studio is working on the third entry in the Knack series, as Knack II was released in 2017, four years after the launch of the first game. The fact that Sony will skip next year's E3 suggests that this mysterious title may be announced during Sony's own shows, but it definitely won't be presented at PlayStation Experience as Sony won't be hosting it in 2019 either.