Players don't have anything to gain by being disinterested and playing below their level, it's not like Bodenmann helping Kloten kick Bern out of the playoffs would have any incidence on the 2015-16 season.
It has happend since the late 80's (although rarely as early as in this case, but it's common that players have new contracts in January already), and there are countless example of players still performing against their future team, the best example being Philippe Bozon signing with Lausanne a few months before sending them to the NLB in 1996.