I believe bitcoin is the future. When all the fiat currencies are going down, I can see the bitcoin go up.
I think that bitcoin will continue to grow even when sometimes it takes a dip, it can take a hit and will bounce back up.
But what would be the reason for fiat currencies to fall down enough that Bitcoin is adopted? I can't think of a single reason why across the world fiat currencies would all fail. Some might fail due to internal country economic policy failure and economic downturn but it would have to something insanely radical to affect the whole world. A more likely idea is that Bitcoin and fiat co-exist for a prolonged period until Bitcoin is recognised to be a superior alternative and further infrastructure is built.