It should load successfully into P4, but if you're using a procedural texture (for instance), you'll be left with nothing but the object colour. The same goes for any shader tree structure. I was fooling around with the Toon shader node last year, saved the figure to the Library, and then decided to see if it would still load into Pro Pack. The figure loaded fine, but it was blank white, since the textures were plugged into the shader, instead of plugged directly into the Diffuse_Color channel.