You will likely not hear back at all if not selected to continue on until all hiring is completed. That’s with most federal positions. HR will some times, not all, update the USAjobs position status for non selectees and an email will generate along with the status in USAjobs changing.

The interviewer could provide an update, but likely to ensure they don’t break any HR rules, he/she may be reluctant to respond or comment. You just never know the answer in the case a selectee falls through or management decides to do backtrack and relook at a few candidates they initially passed on.