Looks like overriding render_done() method works great. But my problem was all about validation. I had field where validator was checking if user exists. If it does not - he was created on that step. So revalidation will alway fail here :). Remvoing this code:
if not form_obj.is_valid():
return self.render_revalidation_failure(form_key, form_obj, **kwargs)
solved revalidation issue at the wizard end.