Normally, I don't support governments investing money into a new venue for a professional sports team (talking NHL, not CFL). What happened in Québec, where Québecor got the City and Province to pay 100% of the arena, is a travesty. Nor am I a fan of the Edmonton deal where the City funded a huge chunk.
Here in Ottawa, a government town that has seen slow growth over the past 4 years, the break-even Sens where able to rally local developers, big builders, investment firms, trusts and even Brookfield to invest in a new arena and surrounding district. They will buy Federal land that has sat vacant for over 50 years for market value, decontaminate the area, cover a metro line and build without asking for funding from any level of government. All they will request is approval for existing grants and tax breaks that exist for companies who want to develop contaminated land.
http://www.ottawasun.com/2016/05/08/going-all-in-on-lebreton-anatomy-of-a-successful-bid
Now if we can do this in Ottawa, there is no reason why the Flames can't do the same for the arena and stadium. Even if the oil sector has suffered through a downturn (which has been slowly recovering), they will bounce back within a few years, as they always do.
BUT, I have to play the devil's advocate. The situation in Calgary is different in several ways. First off, the Sens own their arena, which gives them a 150 million dollar asset to play with. The Saddledome is owned by the City and McMahon by the University. Add in the City's field house fiasco, and the fact that CFL teams (even if owned by the same people as the NHL team) do not fund their own stadiums.
In Calgary's case, I conclude that the City should somehow invest in a new stadium and, at the very least, should do everything in its power to facilitate the planning and construction of a new arena.