He will probably be the creator of the next Warmaster of Chaos-- Emperor's evil twin! I am thinking that the cloned Crown Prince of Chaos would be raised by four "fathers":

Magnus the Red, who would teach him warpcraft and webway navigation; Lorgar, who would teach him public speaking; Perturabo, who would train him in daemonic architecture and siege warfare; and Mortarion would train him in biological warfare. I feel that the Ynnari would seal off the Imperial Webway breach for good, and therefore allow the God Emperor to heal and be more active than ever before-- and set the stage for a twin sibling rivalry so fierce, it would create a new warp storm. If the God Emperor thought Horus was bad, wait until he comes across his twin brother!