First, the word "strain" has no real meaning because it is an artificial concept: Naming a variant a strain is arbitrary: https://en.wikipedia.org/wiki/Strain_(biology) So we have "variant" and "mutant" as more precise descriptions. A mutant of SARS-CoV-2 would get a new name, like SARS-CoV-3. So we are talking only about variants. There are many variants of SARS-CoV-2. 100,000s. The RNA sequence of viruses found on different persons is always a little different. So we are talking about something that happens all the time: A ton of new variants is found every day. The two questions that remain: Is ist possible that a real deadly variant pops up? And can a new variant evade immunity? A deadly variant kills its host and everybody around before it can spread. This is why viruses tend to adapt to the hosts until they do no more harm at all - these variants survive best. The spike protein of the virus is highly optimized for human cells (thanks to the gain-of-function research paid by NIAID and the Pentagon). It is so optimized that most variations render it useless. This is why SARS-CoV-2 is not a seasonal virus and we don't see many reinfections (not the millions expected for a seasonal virus). This means that the virus will run its course and vanishes (like SARS version 1.0). To continue the endless medical emergency they have to release a new virus (mutant).