Can the new 2013 27" iMac function like the Thunderbolt Display? The Thunderbolt display is a really cool external display for thunderbolt-enabled mac laptops, but the sad reality is, all those peripherals and that gorgeous display is useless when the laptop is gone.

My question is, will the new 2013 27" iMac support peripheral passthru via thunderbolt to my 2012 Macbook Air like a Thunderbolt display would?

I would have the following connected to the iMac


Gigabit ethernet
External speakers
Wired keyboard
Wired mouse
USB microphone
USB printer


Would the Macbook Air be able to use these?

When the Macbook Air is connected, I'd essentially like it to operate just like the Thunderbolt display.

When the Macbook Air is disconnected, I'd like the iMac to function as a normal iMac.
For the display, yes:


  Target Display Mode. In this mode your iMac can serve as a display for
  another Mac. This is supported via the Thunderbolt port using a
  Thunderbolt to Thunderbolt cable (not supported via a Mini DisplayPort
  cable)


source: http://support.apple.com/kb/HT5522

For the rest of the devices, theoretically not: 


  7. When I have a Mac connected via the Apple Thunderbolt to Thunderbolt cable (2.0m) via Target Disk Mode or Target Display Mode,
  do devices connected to that Mac become active on my computer?
  
  No. The additional devices will become peripherals for the Mac in
  Target Disk Mode or Target Display Mode. The additional devices do not
  "chain" through the Mac and its other Thunderbolt port.


source: http://support.apple.com/kb/HT5219#target

Hope this helps (wouldn't it be neat?)