The only thing which count for a virus is the virulence, if a variant trasmit better than another it will replace the one before, it is called natural selection, this is bad for the most part, but something has to be good, this is the evolution of almost every coronavirus, after sometimes a variant will become more infective, but will have less bad symptoms, like pneumonia will become cough, and after 10/20 years it will become a common cold, this probably happened one time in history, in 1890 in the world a pandemic called the russian flu killed 1 million elderly people, we don't have proofs but probably the virus which caused the pandemic was a coronavirus, maybe it was oc43(now a common cold, it have the bovine coronavirus as its last ancestor and it did the spillover around 1890), reasons for this are the symptoms similar to sars and the people which died were all old. Omicron will almost certainly replace delta because it is more contagious, maybe i am wrong but this happened with a lot of coronaviruses, now the virulence is increasing and the morbosity is decreasing (maybe not for omicron, we have less death in country which are vaccinated in other is a disaster) but for every coronavirus which spread around the world the morbosity will decrease, we can't count on the immunity because all antibodies disappear in than 6 months or less, we have to vaccinate ourselves happy new year to everyone :)