The specific hurdle mentioned in the article is that they only live in the tropics. However they do mention research looking at using wood ants to protect Maize or to control winter moths in temperate regions.
Well right now the entire bitcoin economy is valued at $1.6B so if a bitcoin rises to $1M the bitcoin economy would reach $12.3T . I'm no economist but that seems like it might be an unrealistically huge percentage of the world economy. I really don't think there's enough investable money in the world to get there.