I support multiple difficulty levels. I was originally thinking the current difficulty level would be the hardest, but maybe the current level could be the mid-level and one more and one less difficult added. This could give the super pros something and widen the games appeal to a much broader audience by making the game more accessible to the casual player.
As others have said, you could actually create a higher difficulty level by tweaking or eliminating some of the shot helper tools in the game. Just need a button to toggle them off, still takes work, but less than programming an entirely new difficulty level. Maybe over time get some of this. The new relationship with the PGA should strengthen the company's commitment to the market for a golf game.