A more redundent power installation, if one generator would fail, all propellors could be powered from the remaining generator(s). Plus the aerodynamic advantages of a much a more flexible system layout
Plus a lot of possible prime energy sources (besides the extension cable mentioned in a post above and the obvious gas turbine generators APU-like ), like fuel cells - with no rotating parts, and many electricity storage solutions -yet in the developing stages, plus...plus.... but all of them after 5 -10 years