The Federal Council announced today that they have started a consultation with various measures in regards to the current comeback of Covid-19. One of the regulations on their list is the reintroduction of a mask requirement. This would be for indoor events with a certificate requirement and thus also count for hockey games.
Some cantons have already made masks for events obligatory again, such as Geneva and Bern. With the Federal Council's consultation, masks would return to all hockey stadiums in Switzerland.