This week Ryan Murphy promised EW that we would learn who he i, 100%. Here is the quote:
And next week is the Rubber Man reveal right?
... We reveal 100 percent the identity of the Rubber Man. We also show people how the Rubber Man came to be. You see, Where did the costume come from? Who is it? Why are they doing that? What is the Rubber Man’s goal? It’s also a great episode for Zach Quinto, who’s amazing in it...
My best guess? I think it's Constance's husband, that she shot dead. He is so the type! Let me know what you think in the comments area.
And for grins and giggles, check out how the rubber man suit was purchased in the spoiler video(its the reason I discounted Zach Quinto as the rubber man, way too easy. Plus, he would have really had to do some funky acting to kill himself that way... heh.)