Oh, c'mon. When you've got the whole symbiote thing built into the Dax character from the beginning, how do you NOT play that card if the opportunity arises? There's almost no point to having a Trill regular if you don't have her/him get a new host at some point. It's like having a Vulcan and never doing a pon faar
plot . . .
introducing a new Dax when Terry Ferrell sought greener pastures would have been a crime against storytelling.