The argument for waiting is always the same: next year there will be better tools, more budget, a calmer quarter.
Is it cheaper to migrate later?
Better tools do arrive every year. So does another year of data in the old system, another set of processes built around its limitations, and another cohort of people who only know how to work that way. The migration does not get easier as it gets later. It gets heavier.
The cost of moving is proportional to how much history has to move with you. That number only goes in one direction.