Spoilers ahead, especially if you haven't seen Iron Man 3 / Captain America 2 / Agent's of SHIELD season 3.
When I say the Mandarin I am not talking about Trevor Slattery, but Aldrich Killian.
Towards the end of Iron Man 3, Aldrich Killian says:
"You see, I've moved on. I found myself a new political patron, and this time tomorrow, he'll have your job."
Who is this new political patron?
I have heard a theory that Gideon Malick (who was on the World Council in Avengers 1 and one of the heads of Hydra in Agents of SHEILD) was after the Extremis project. This would explain how Hydra had access to the Extremis technology at the beginning of season one of Agents of SHEILD, but I haven't found any evidence to support this yet.