All it takes is one country like Switzerland legalizing cryptocoin tumbling. You send your bitcoin to a single address along with millions of others, and it sends out to millions of addresses different values, with no traceability between the sender and receiver (if done correctly, such as batching all transactions over a month into a single event). It would be used by many legal entities also in order to hide their activity (rich people don't want their financial activity known to the public even if it's completely legal).