I believe a HYBRID solution where institutions and decentralized companies work together to ensure one another without interfering
A "middle" man if you will between governments and D-companies
This of course must happen through public consensus like Parlaments or Congress and that alone could take years , roughly 20 years or so like you said but am betting on tech progress to beat the clock and would like to say 10 years
Tech progress is the fastest industry humanity have ever witnessed...
So things like Lightining network, Quantum computers etc. could be a disruptive force in terms of creativity, possibilities and of course, speed