Kudos to Circumflex, who pointed out a MacCentral item which reports that Mumbo Jumbo has hired Duane Johnson, a programmer known for his work porting games to and programming on the Mac. An excerpt:

In addition to the original development of Myth III, Mumbo Jumbo is managing MacPlay's game conversions for 2001. It appears that those efforts are what Johnson will be helping Mumbo Jumbo with.

So it appears he won't be directly involved with Myth III, but it seems unlikely that he would have nothing to do with it. Always good to see a bit more commitment to cross platform development.