So far, Crash Bandicoot 4: It's About Time has only been announced for PlayStation 4 and Xbox One, and the developers haven't said anything about versions for the next generation. But this doesn't mean it won't come, quite the opposite, as ESRB (the American PEGI counterpart) has now rated the game for Xbox Series X.
And this is something we would consider a fairly solid sign of things to come. But why hasn't Activision announced this then, as others have? A reasonable guess is that it isn't a free upgrade, something Activision has been very reluctant about. As such, it probably wants to sell as many Crash Bandicoot 4: It's About Time copies it can for PlayStation 4 and Xbox One - and then sell it again in upgraded versions for PlayStation 5 and Xbox Series X.