In spring 2011, Bugaboo will introduce the Bugaboo Donkey. It's the first double stroller for Bugaboo and it's being billed as the first ever "mono-duo–mono convertible stroller". Which means it can convert from a single stroller to a double stroller and back again with three easy clicks.
In single form, the Bugaboo Donkey is 23 inches wide, the same width as the Bugaboo Cameleon. In the double form, the Bugaboo Donkey is 29 inches wide, making it the narrowest (luxury) side-by-side duo stroller.
The single form features a single seat next to a storage basket, while the double features two seats or a seat and a bassinet. I don't know about two bassinets or car seats at this point.
I don't have much more info that. Hopefully I'll get some at ABC next month.