People forget that Denver is an incredibly crowded sports market. People here have options.
We're the smallest city with a team in all four big leagues, plus we have MLS. And we have the flagship franchises of both pro lacrosse leagues (Mammoth have averaged 15,000 fans a game for 10+ years, Outlaws 8-10K for 8), CU and CSU football and basketball, plus all the other minor league and college programs in the state (DU, Colorado College, Air Force, Northern Colorado, Metro, CHL, ECHL, minor league baseball, etc).
History shows that whatever sport you're selling in this market, people will buy it as long as you have a good product and treat the fans with respect.
I have no doubt the Avs will have bigrger crowds next year. The Nuggets crowds will probably suffer, but it won't be anything to panic about for them either.
This city is too small to sell out every game for all its teams. The Broncos will always reign supreme in this market and the Rapids, Mammoth, and Outlaws will always have their niches. Whatever team gets secondary focus between the Avs, Rockies, and Nuggets will always depend on which of them is winning.