I'm assuming that eventually someone will put out a high-output LED headlight that takes 4 to 6 standard AA NiMH cells. But even if not, heck, the Trailtech HID comes with a 4000 mAH LiIon pack with a smart charger for $190, complete. LEDs should be cheaper than that.

Really, as far as I can tell, the real advantage of LED over HID is durability over long periods of time. HID is actually more efficient in lumens per watt than high output LEDs, but LEDs are going to last longer. Also LED doesn't need quite the circuitry that HID does.