We don't yet have a clear picture of how necessary booster shots will be. Each mutation that impacts antibody reactivity also has a chance to impact infectious

We don't yet have a clear picture of how necessary booster shots will be. Each mutation that impacts antibody reactivity also has a chance to impact infectiousness, and the proteins targeted by the vaccines are large enough that it isn't trivial to predict the outcome. So we might need to do boosters, or we might be fine with the vaccines we have now.