It would depend on the pace of the rollout, how quickly we can get Pfizer supplies, if Novavax is approved and when supplies of that arrive etc.
Under 50s in 1A and 1B can get Pfizer now. Once the exception groups (such as those worker in border control, hotel quarantine, COVID wards of hospitals etc.) and those in 1A and 1B eligible for Pfizer are closer to completion they will presumably start letting under 50s in 2A (which would be the remainder of 2A) get Pfizer too.
That leaves phase 2B; and phase 3 (if needed) to go after that.
Once hopefully international borders are planned to be reopened the need to get the vulnerable over 50s vaccinated with whichever vaccine they will take (if they haven't had it already) will become much more urgent. The risk to them would have to be weighed against the much lower risk to the healthy under 50s in phase 2B, and the kids in phase 3.