[mycookie]

Also, just because the GPU can power 4K doesn't mean it will for a reasonably small amount of power, such that the MBA can continue to pull a 12-hour battery life.

[FootballMuse]

If you are plugged into a 4k monitor, you are probably reasonably close to a power outlet.

[lloeki]

Theoretically, Thunderbolt is capable of being your power outlet.

[estel]

Yeah but if you're powering your 4K monitor from Thunderbolt, I doubt you'd get that 12 hour battery life either :D