Why?That would make no sense giving the ending of IM3.
I don't think we explicitly knew he's just magically over the PTSD.
He may have given up on the "Iron Man" suits and whatnot, but why is it a far stretch to assume he won't keep creating? JARVIS is his own invention, why not more AI? Why not more AI bodies etc? Even if we never see Tony Stark back in an Iron Man suit, the ending of IM3 still allows him to keep spending time with Pepper while doing AI/research/animatronics from the comfort of a Malibu mansion.