Sadly, the aura seem to work only on Riolu (not sure about Lucario though). I wonder if he trains himself enough, Satoshi would be able to communicate with all monsters if he knew about Riolu's feelings during last week's episodes.
Maybe with a little more training it could work with other pokemon, then Ash could be like the frontier brain Anabel. That would be awesome, Ash could score some extra cool points with Dawn.