Impact?
For TPB, not much for a long while. This verdict is being appealed already, so this is just the end of act I, with act III being the supreme court.
Until then, TPB will stay operational and the four guys will remain free.
For filesharing, it might facilitate a hastier demise of the bittorrent protocol as the mainstream solution, and more focus on developing better technology. And darknets.
Legally, it sets somewhat of a weird precedent, since the four defendants were convicted of "being accessories to copyright infringement", although no convictions for the main crime, the actual copyright infringement, exist. It is simply implied. Also, since all that TPB does is provide an infrastructure, this can also open the door for lawsuits against other infrastructures that can "assist" in spreading copyrighted material, even ISP:s themselves. Some antipiracy groups are already using vernacular like this, claiming ISP:s are "using a business model that is based on creating the possibility to share files illegally".