They will usually come down on their own within 2-5 days, typically at night when nobody is around. However, a few won’t, especially if they are not used to climbing. Since it’s been 4 days already, I would probably call animal control.
As an aside, injuries caused by falls are well documented in cats. This is quite common in urban areas with apartments and is called high-rise syndrome. While it’s true that cats can survive many falls, critical injuries can occur with falls from heights as low as 2 stories (24 feet). The severity of injuries increases linearly with height up to about 7 stories and then becomes constant, as Indian indicated. This is because cats reach terminal velocity (aprox. 60 mph) after falling about 60 feet. Beyond that, they are no longer accelerating, their vestibular system is no longer stimulated and they assume a relaxed posture. This probably increases the surface area of the deceleration forces, much like skydivers are taught to fall. Nevertheless, serious injuries, including chest and spinal injuries are a real risk with such falls -- so knocking the cat out of the tree is not a good idea.
I hope everything works out well for your kitty.