Board Thread:Boruto Discussions/@comment-28341973-20160827204918/@comment-1512913-20161125220426

Considering that Mitsuki's original name means 'snake vessel' it's a nice hint that Mitsuki was created with the intention to become the perfect host body for Orochimaru. If this is true, then the only reason why Orochimaru wouldn't take over right away, is if more things need to be added to Mitsuki first, like DNA/chakra of Naruto and Sasuke.