They don't have to splice Legacy with anything it's complete. I'll quote what Mike said on his forum:

It's going to film to get the quality of film that only film has - grain, curve, etc. The master files are being adjusted so that the negative is correct, meaning that if viewed, the original DCP would look different, not "better."

Prints will be struck directly from a negative, and yes there will be multiple negatives, this being the advantage of having a digital source.

Legacy is ready for a negative to be made and prints struck!