Even if the games don't need overtime, the NHL will do a dress rehearsal of the new rules during 3 Flyers preseason games.
In case you missed it during your summer hockey slumber, the NHL will completely overhaul the overtime rules in 2015-16, switching to a 5-minute long 3-on-3 format.
Yes, overtime will be completely 3-on-3. No 4-on-4 at all. All the details are here. The idea is to cut down on the number of shootouts by making it easier to score during the OT period, although games still tied after OT will go to the same shootout we've come to love and or hate.