Bidirectional A*: is an update of the distance estimation feasible while searching?
I think I have found the answer in the paper and it is indeed not just a replacement of the potentials:


  Now, if we want to replace p_f and p_r (forward and reverse potential) , all we need to do is change
  the keys of the labeled vertices for the two searches appropriately
  and update the priority queues containing these vertices. This takes
  time proportional to the number of labeled vertices at this point.