That's something we'll have to figure out in that big reunion council we keep talking about. ;-)
I think +John Cassian and +Augsutine will be a relatively low priority for the blessed council. If we can get to define our mroe important misunderstandings the rest will fall in place.
I am not very familiar with +John Cassain, but I doubt that he advocated such unorthodox beliefs as Pelagius (allegedly) advocated, i.e. that we don't need baptism.