Yep.Probably only an issue for a few weeks if it's going to become the dominant one right? Once it is don't we just assume like we currently do and run the full sequencing to monitor for others?
Alpha had the same S gene drop out and it was used as a quick way to track its progress versus wild type. When Delta came along, which has the S gene, the same method was used to see how it was outcompeting Alpha.
The rough guesses I’ve seen have Omicron dominant over Delta in Uk in early Jan based on SA spread but given the different variables on weather/vaccine/natural immunity etc hard predict without some more data.