It really depends what kind of professional photography OP is talking about.
Sure, professional photographer can take a gorgeous artistic picture with small p&s, but he cannot shoot, for example, a NFL game with that.
I can guarantee that I can take better NFL photography with 1D Mk.III & 300mm f/2.8L IS than a professional photographer with Canon Ixus.

All depends on what kind of photography OP will take.