No!  For 999 out of 1000 dents, they will not come back, ever.   Some times we are asked to repair dents that really shouldn’t be repaired with paintless dent removal.  These severe dents have actually stretched the metal of the car.  When we repair these dents, the metal actually comes out too far, creating a slight bulge.  This is the kind of dent, which if slightly hit, can pop back in.    These dents don’t usually repair well, and I steer people away from repairing them.