I'd love to see Apple do some serious work on the battery side. If anyone's equipped to do it, it is (though I'm less certain of this after the "sapphire" debacle). You wouldn't believe how hard it is to actually get new battery tech to market: I've probably seen a dozen start-ups pitch technologies that could substantially improve capacity, longevity, safety, size, weight, manufacturing cost, or a combination of the above. None have yet succeeded at scale.