In the new user interface, it is possible to rotate the map while holding Alt+Shift.
The rotation is also automatically calculated after you assign first two ground control points on a map!
This feature will make the georeferencing easier and more convenient for the users. The rotation feature is now developed, applied in the Cynefin pilot project (http://cynefin.archiveswales.org.uk/), and it is going to be a part of the next generation of Georeferencer service.
Following short movie shows the rotation feature: