Force Pit Member
No, it was never confirmed before. It has been confirmed now. It was implied however that they monster trio all had various degrees of haki! But Luffy is the only one with Haoshoku haki...well Zoro could get it later on as Rayleigh had it and he was a first mate too. And it goes without saying, that the monster trio, the strongest force of the mugiwaras need to have haki to survive in the new world. More logias, more Vice Admirals, that all have haki etc. They were also the ones that trained under people that presumably had haki (Rayleigh), Ivankov and Mihawk.