As written, the HPA provides for a refund of the stamp tax for suppressors purchased after October 22, 2015. This is so people don't completely stop buying them in anticipation of this passing. https://www.congress.gov/bill/115th-congress/house-bill/367
I really hope this passes. I have an annoying uncle that stops by during hunting season every time there's a shot in the area to see if I got anything. A suppressor won't get rid of the sound completely, but it will help.