Here are the events that lead up to where we are in the NHL. If the NHL gets past this lock out it needs to have a big change going, or hockey will die out.
There are two was to keep hockey around. Either the NHLPA can agree to everything, and work with the NHL to make it better (like the NFL). Or the NHL owners should close their NHL teams and a new league and new hockey teams. If one of these two things don't happen NHL will lose it's spot as the number 4 sport (like thats much to brag about.)
Why? Well for one, many (most) NLL (national Lacrosse League) team owners are NHL owners. And NLL is packing the arenas. So if hockey is not a profitable sport, I can not see why the NHL owners just don't make NLL teams instead.
Arena football is looking to put in another strong year this year. They have the tv contract, good owners, and the backing of NFL. I could easily see this becoming the fourth largest sport.
Then there is the sport of the rest of the world- soccer. The MLS looks to be pulling out of a lull in the business, with some teams even getting soccer only stadiums (Columbus and DC) and many more talking about or building them (KC is talking about it to keep the Wizards). If MLS can get a bit more publicity, i don't think it would be that hard to make it work well.
In any case, there are many leagues trying to figure out a way to jump into the #4 that the NHL is basically giving away. Let's hope the NHL can put up a fight for it... please...