L’étape prochaine d’entretien

As an answer to your question and comments, I would say that, in that context, on verra ça lors de l'étape prochaine d'entretien is understandable but not quite perfect. First, say prochaine étape rather than étape prochaine.

There's a little grammar subtlety. If you say on verra ça lors de l'étape prochaine d'entretien, then one could think that the first and the second stages were interviews.

If you say on verra ça lors de l'étape prochaine de l' entretien, then both stages are included in the term entretien (which therefore consists in two parts).

But if the context is that the first stage is not an interview but the second one is, then I would suggest to split into two propositions, like On verra ça lors la prochaine étape, celle de l'entretien, or (more idiomatic) on verra ça à la prochaine étape, l'entretien, or even on verra ça à l'entretien.