First, let’s look at the nature of the beast, because that’s what Prime 4 is - a hardware beast, ment to perform on its own, without the need of an additional computer, but offering additional functionality as a controller too. Denon DJ has a long term commitment with Serato and that means that support for other software platforms requires some diplomacy behind closed doors. Maybe support for other software platforms, like Virtual DJ, will come in the feature or not, but that is up to Denon DJ and third-parties to decide. For the moment, Denon DJ commitment is to improve Engine Prime functionality and to refine the Prime series hardware functionality.
So, at the moment, if you like Denon DJ Prime 4 features and feel comfortable with it for what it is, you can enjoy it very much and adapt to the way this hardware works.
If, on the other hand, you feel that working with Virtual DJ is essential for you, maybe it is better to look at other alternatives.