As far as I can see:
1. If the purpose is to generate "power", remaining of course within the limits of electrical safety, traditional hub dynamos might become somehow obsolete
2. Traditional hub dynamo is by its own design and construction not "flexible" at all
3. Conversely, the generator presented above can modulate the power just adjusting the distance (airgap) between rotor and stator, or adding/removing magnets if you like!!
4. In case of disk brake you still can install it onto the front wheel
5. The big drawback, imo, is represented by vibrations; the only way to overcome this problem is redesign the coil-array and give to it a "U" shape to encompass the magnets passing through it