I'm sure there's a place for AI to transform our world economy. It may not be directly, as Blockchain technology handles transaction management. AI could take part on the decision making of the world's economy, such as restricting or granting access to the digital economy by using facial recognition, voice recognition, and more. On the other hand, Blockchain will be responsible to make sure transactions are not double spent, and are as secure, transparent, and reliable as possible.
Given how Bitcoin and Blockchain technology have grown over the past years, it's no doubt that the world's economy is shifting towards being digitally distributed across many computers and devices worldwide. As for AI, its growth rate is slower than the Blockchain. It will get there once it becomes mature enough for the mainstream world (which could take a couple of years from now). In the case of hacks, I doubt if it'll be possible to hack and game the system, as Blockchain technology has proven to be secure and resilient against attacks (like in the case of Bitcoin). AI could gain the strength of Blockchain's computing power, to protect itself from hackers.
Nevertheless, either Blockchain or AI (or perhaps both) would greatly contribute to our world's economy one way or the other.