If after every tempest come such calms,May the winds blow till they have wakened death,And let the laboring bark climb hills of seasOlympus-high, and duck again as lowAs hell’s from heaven!
It is almost like he is welcoming the Tempest, because he feels as if nothing can ruin it now, with Desdemona -- this is a literal inviting of Iago to come ruin it. It is to show that his defencelessness and overconfidence invites the inner beast within to come rupture it.