[Colin2B]

I heard a version from the Swiss expert Pitte that in the future COVID-19 can become like a common cold. I hope he's at least a little right

He could well be, but which one?
The mutations are like a branching tree with each branch mutating separately and, as @Bored chemist says, a branch can just as easily mutate into something more harmful. The question is which one or ones become dominant.
There is currently investigation into whether Omicron mutated from Delta or from an earlier strain.

[Bored chemist]

It's true that, over time, viruses typically evolve to become less lethal to the host.
But the reason for that isn't good news for us.
The mutation process is random, the outcome may be a virus that's more lethal or less lethal.
If it's less lethal, that's lucky for us.
If it's more lethal it typically (on average) kills the host before the host has a chance to pass it on.
The thing that stops viruses becoming more lethal is deaths among hosts.

Also a virus that initially only killed something like 1% of the hosts is not under huge pressure to reduce that; it's already 99% "successful".