Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_3_5 like Mac OS X; en-gb) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8L1 Safari/6533.18.5)
I too would love to get one.
Can the thunderbolt iMac drive two external displays?
Yes. Although the 21.5-inch would need one of the displays to be an Apple Thunderbolt Display because it only has a single Thunderbolt port. The 27-inch can drive any combination of two DisplayPort 1.1a displays and/or ATDs.
I'm not sure about how four displays would work with the 27-inch if at least two of them were ATDs. I believe the TB controller only has two DP inputs, so you might have issues addressing them all.