Oops. Yes. I didnt click on finish 
Because some wizards will let us know if its enabled for PSM before proceeding to final step. Nevertheless, still wonder why it was throwing that error. Weird!!!
Because, I could able to create a comm. scenario (this time clicked on finish 
) and activate successfully in FP4.0. Also the documentation of QuerySupplierIn says its released (of course we cant believe the docs provided by SAP sometimes).
@Tim: May be you can also create a incident for this and let us know what is the update 