There are a few different scenarios for Omicron.

One is that Omicron is so transmissible that it spreads around the world and outcompetes all other variants, including Delta, so that, in the future, all new viruses are descended from Omicron. This scenario happened in mid-2020 with a variant called D614G (this was before variants were given Greek names) from which all subsequent variants are descended.

Another scenario is that Omicron spreads in some locations but ultimately turns out to be less transmissible than other variants and eventually falls out of the picture. This happened with Alpha and Beta in the first part of 2021…

If Omicron causes a rise in cases but less severe disease than Delta, that would certainly be good news. But if it spreads widely, it could still send a large number of people to the hospital. Also remember that it’s possible Omicron is at least as severe as Delta in people without immunity. We also don’t yet understand the long-term health consequences of having Covid-19, and it will take weeks to understand how Omicron affects groups of people with different levels of immunity.