Cynical view: maintenance burden will stay roughly similar, because fault rate is not ultimately driven by technology, but by how much the market is willing to bear. In other words, companies under competitive pressure will cheap out on materials and cut corners in the manufacturing process, making their cars as faulty as they can get away with, and unless something changes structurally in the market (e.g. death of used cars market, much less car ownership, much more leasing), the existing fault rate of petroleum-powered cars tells you what the market is willing to accept.