Fans will always return. When the lockout happened back in 2004-2005, fans returned when hockey did the fall of 2005. Not all fans will immediately come back, some may be hesitant but eventually all the fans will come back In some cases the fan base that comes back might even be more than what the original fan base was. When a sport is out either for a season, or a lockout, or whatever the reason people miss it, so when it come back you can usually count on a high attendance.
The NHL will keep their fans after the lockout. NHL fans are some of the most loyal fans in sports. They've been through a lot over the past few years and have stuck it out. Many of them are passionate about their team and the gain. The NHL will resume as if nothing happened.
I think most fans will return to the NHL despite the lockout. While some people will be irritated and may stop watching hockey, the die hard fans will come back to support their teams the same as they always have. If someone has spent yeas following and supporting a team, they won't give them up over one lockout.
Hockey fans are a different breed, they are loyal to their sport. They are no doubt angry, they no doubt feel betrayed by both the players and the union but when it comes down to it, they want to support their sport and support the unique culture that comes with hockey.
The NHL will retain the die hard fans, but those on the fence are gone. In the last 20 years there has been a strike and 3 lockouts in the NHL. That means every 5 years there is a work stoppage so millionaires and billionaires can argue over money. Ridiculous.