It's about maximizing value. If the Jays and Jansen can come to a reasonable extension agreement, then maximizing value is to trade Kirk or Moreno. If they can't, the maximum value is by trading Jansen. Extending Jansen and trading Kirk or Moreno can be done in parallel, the trade being the conditional piece.
Of course, if someone wants to overpay for Kirk or Moreno, then you just do the deal, extension or no.
Jays are in a unique situation of having 3 starter calibre MLB catchers, and hence value each catcher less than other teams. They can parlay that into a fairly significant team improvement, even more so if they look after the player salary end at the same time.