There is no way to change the camera while the animation is playing, that is why it stops. The reason is that any movements (unless you turn the camera key red) will be taken to be a frame to be keyed and Poser does not do real time animation (yet).

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13