I think we can rule out Mark Zonder for sure from the possible replacement list. He posted this on his Twitter / Facebook account:
"OK, as much as I appreciate all of the calls, emails, tweets etc......no, I have not been approached by DT for the drum position. I am thankful for all of your good wishes and nice compliments, but as of now, you guys know as much as I do. I do think it would have been great to at least work on a song and track it with them, but so it goes. Thanks again for the support."
I'm still betting on Thomas Lang.