The kid in a way reminds me of a young Wawrinka so there is hope for him. Stan was always dangerous but mentally was a basketcase and not a big-match player until his late 20's and I think that's where I see Thiem right now. And the good news is he is still just 23.
He has also been one to take advantage of the current landscape, i.e. Fed is out, and Nole and Andy have been terrible more or less. If I had to guess I'd say Dom wins 1 slam at most in a few years, there are better young talents (Zverev and Kyrgios) so the longer it takes the more unlikely it seems.