There are several arguments supporting the idea that covid will become like the common cold, it is not a generic "all viruses turn into the common cold".
We already have 4 endemic coronaviruses that cause common colds, and we suspect that they started as deadly pandemics too, which were historically reported as the flu. Many specialists suspect that the OC43 coronavirus caused the 1889 "Russian flu".
Covid seems to follow the same path: a disease that is mostly harmless to the young but potentially deadly to older adults with no acquired immunity. It is likely that in a generation or two, everyone will be infected at a very young age, building immunity and occasionally get breakthrough colds. Breakthrough cases already look a lot like colds.
You give two arguments. One is that some colds in humans are caused by coronaviruses. But on the other hand, coronaviruses cause severe and fatal illness in livestock and are not getting attenuated.
The second argument is that over a century ago, an epidemic might have possibly been caused by a coronavirus, and might have possibly become a common strain of the flu. This tenuous and unprovable line of reasoning is exactly what I see as wishful thinking.
We already have 4 endemic coronaviruses that cause common colds, and we suspect that they started as deadly pandemics too, which were historically reported as the flu. Many specialists suspect that the OC43 coronavirus caused the 1889 "Russian flu".
Covid seems to follow the same path: a disease that is mostly harmless to the young but potentially deadly to older adults with no acquired immunity. It is likely that in a generation or two, everyone will be infected at a very young age, building immunity and occasionally get breakthrough colds. Breakthrough cases already look a lot like colds.