Despite limited knowledge about Omicron, it seems quite likely it will spread to significant portion of population before updated Pfizer vaccine is available. That's the reason why I prefer third dose to waiting for updated vaccine. See the calculation below:
Facts and estimates:
1. Pfizer states they are able to update vaccine in 100 days: https://www.businessinsider.com/pfizer-vaccine-update-100-days-omicron-variant-resistant-2021-11
2. Doubling the cases every 3 days seems to be an optimistic (well, “optimistic”) scenario: https://www.reuters.com/business/healthcare-pharmaceuticals/omicron-cases-doubling-15-3-days-areas-with-local-spread-who-2021-12-18/
Exponential model for the optimistic scenario: In 99 days, the number of cases will double 33 times. That means 1 case can make more than 8 billion (2³³) cases in 99d.
This will not happen, as post-infection immunity will slow the spread noticeably down at some point. However, just the fact we are going to reach the point implies a significant portion of population will have been infected before new Pfizer vaccine is available. Waiting for updated vaccines without significant countermeasures in the meantime doesn't look as a good idea.
What about other vaccine vendors? Maybe Moderna will be somewhat faster, but I strongly doubt they'll be that much faster. Others are probably out of luck – I don't think non-mRNA vaccines can reasonably compete the development speed.