not at all ... no coach plans for them not being around anymore. They plan for future seasons with them being in charge of the team ... especially Wayne Bennett, who before last year, would never even contemplate the slightest possibility that he would leave the club on anything other than his own terms.
the coach may not make the final decisions on contract value, but they would have a big input on what they believe the player is worth. how important said player is to the coaches plans would also be given serious consideration when negotiating a contract. obviously the club's management have to work all that into the clubs salary cap position.
but the point is, a coach, especially someone like Wayne Bennett, would have a massive say on contract length (in particular) and price.