It needs to be said that Sony is struggling at clarifying some of the issues surrounding PlayStation 5, as can be seen from the confusion with exclusive titles: the alleged (and short-lived) confirmation of PC edition of Demon's Souls and the rather late announcement of the release of Spider-Man: Miles Morales and Horizon: Forbidden West on PS4. Even longer we had to wait for the clarification of the situation with another game. Only now have we received official confirmation via Twitter that Ratchet & Clank: Rift Apart will only be released on PlayStation 5.
This should perhaps not come as a surprise, given the assurances of the devs that it is vital to use the power of the PS5 on subsequent presentations of the game. But the same could be said of the new Spider-Man and Horizon. Either way, the new Ratchet is to be considered the first original (i.e. not a remake, remaster, etc.) and truly exclusive AAA game for PlayStation 5. Another thing is that we'll be waiting for it for quite a while. Ratchet & Clank: Rift Apart will be released next year.