What happens to Housing Benefit if I'm migrated before getting my pension?

Would I have to reapply for HB again once reaching my pension? I really don't want the hassle or stress. But I'm 8 months off my pension. I share HB with sibling who's already on pension. & don't want to mess up their claim either. If it's just a few months off my pension and I decided not to claim UC and lived off my PIP till then could I stay on HB on grounds of low income or would I still have to reapply? I thought I was at least and at last getting to have a smooth ride until my pension after all the turbulent years of applying for ESA & PIP endlessly.

Thank you. Would you get in touch with them now before migration? I may be lucky and not get migrated beforehand but worried what will happen if I do.