I would like to see products with PBR shaders. That has been sorely lacking. I'm not sure about the "only" part. Going that way you will stand out in the marketplace. However, having both will allow you to sell to the broad customer base. I understand how much of a pain it is to set up two sets of materials. It's a lot of tiring work to get it right, but having no idea that anyone will use it. If you do go to PBR only, expect backlash. A lot of DS vendors switch to Iray only materials. The 3Delight users bitterly complain on the forums and will not buy those stuff.