"That said, this initial immune protection might wear off over time, as studies hint that immunity to seasonal coronaviruses may be short-lived, Live Science previously reported. Immunity to COVID-19, whether gained through natural infection or a vaccine, may similarly wane through time. "
The loss of immunity to many of these viruses results from an inherently "poor" proof-reading mechanism in its RNA polymerase, if I recall correctly. This results in numerous mutations, a definite advantage long-term for the virus. It can make many mutations that are "non-functional", but also enough that work to continue to infect and survive, endlessly into the future. This is the reason why this particular virus must be eradicated, if at all possible.
It seems likely that every viral genome coming off the "assembly line" has some mutations. Some virologists should team up with some gene sequencers and determine the variation in this rate of mutation and compare them to other coronaviruses. That might provide a clue about how much we can expect this virus to change over time. Alternatively, the sequences from millions of infected people could be compared, and a mutation rate for various viruses established.
Does anyone have any idea about the potential of antigenic-shift between this new virus and its "common cold" relatives, and how that might play out?