I believe that MLS could survive under certain circumstances, namely a suitable stadium. At this point in time, I'm not overly concerned about MLS in Calgary, just mostly pumped about the arena and surrounding district, promised to knock our socks off.
But, for MLS to work, the stadium needs to be able to accommodate smaller crowds without feeling empty - that is the key. I don't love BC place for many reasons, but the way they accommodate whitecaps for roughly 20k spectators is done very well.
I think a Calgary MLS team would get 20k supporters for the first year, and dwindle to a regular crowd of 12-15k. Which is a great number for MLS. Soccer has global appeal, and the number of immigrants arriving to Calgary grows. And MLS is CHEAP compared to hockey.
I think if they test the market with a semi-pro league, the numbers will be abysmal. It really needs to be all or nothing for it to work IMO. The best league (MLS) or no league. It's easy to get behind a team when it's best on best, and you have major stars like Giovinco, Kaka, Villa, Pirlo and others coming by. Becks should come out of retirement, he could probably attract an extra 5,000 female (male?) fans per game alone
