He's confirmed that he will be using McDiarmid's voice, but restoring the original dialogue as much as he possibly can, which is supported by what we hear in the trailer, which is mostly the original dialogue with McDiarmid's voice. He also mentioned that he doctored the "Yes ... " at the end so it sounds like he's saying "Yes" twice, when really it's the same one, just digitally altered. I doubt he'd go through that much work just for the trailer if it's not going to be that way in the final product.