True, they need a plan in place. If they have a successor in place they can eat as much of his remaining cap hits now which means they can backload some of those other deals for when Dak is gone.
On the flip side if they think Dak will age well they could even look at getting him another extension in place soon which could significantly lower his 2027/2028 cap hits and give you extra years to delay that pain.
Both paths have good arguments, but at some point within the next 9 months the cowboys probably need to choose one.