Lo and behold, it worked! Here's my MacBook Air 11" running its internal display and two external Thunderbolt displays at full resolution.
I sent the picture to popular Mac blog 9to5mac and they decided to write a story about this. (It's interesting to see your name on a Mac rumors site.)
This is a developer's dream come true. If you want two large displays - one for code, another for documentation - you no longer have to lug around a 15" MacBook Pro.