That may well be true. Certainly, and reserving judgement on exactly what this means, nobody who could lead it quite like Stallman.
But, I find the implication hard to accept.
It would be to say that Stallman’s continuing presence is essential to the success of free software; surely a frightening responsibility for any one mortal person to carry through their remaining years!
Free software has had success as a movement. To believe otherwise is to take away more than just Stallman’s position, but his entire contribution to our modern society!
That means there are others who will, and for a fact do already, take care for the well-being of the GNU projects. Not all of these will believe in everything Stallman has said or represents, and things would certainly change without him.
A large and successful movement lives beyond its founder, and grows to challenge the new status quo. If it fails to grow, new movements fill the vacuum.