Yes, it’s speculation with circumstantial evidence for now. The Korean health authorities said that the virus could reactivate with re-emergence of symptoms (but milder). Re-infections in such cases are not likely, they said.

I think ‘dormant’ depends on how one interprets it. Most dormant viruses like herpes virus family (affecting 60–90% population worldwide) rarely cause symptoms. At least other coronaviruses (not SARS-CoV-2) can enter dormancy. Whether this applies to SARS-CoV-2 is speculations for now. To prove it experimentally would require some time.