Yes the builder will estimate the taxes and adjust accordingly even if taxes are not assessed. Tax assessments for a new condominium building could take awhile (sometimes even a couple of years).
Make sure to hold on to your statement of adjustments and compare the builder's estimate of taxes to your actual property taxes. If the builder over estimated, and therefore took too much in their adjustment, they are under a duty to adjust vis-a-vis their undertaking to readjust which should have been delivered to your lawyer. If the opposite is true, then you may be under a duty to readjust and compensate the builder!
Hope that helps!