I am not particularly worried about a sulfur shortage. My understanding is that before it was produced as a byproduct of fossil fuel refinement, we used to mine it by drilling wells, pumping steam into the ground, and pumping out the molten sulfur (video below). With increased oil and gas production, mining became uncompetitive. Maybe we will just have to start mining sulfur again in the future to meet demand, but I don't see us running out. 

https://youtu.be/1wswsLGRl-o

AXP