stluke,
I am not sure if it has been mentioned before on this thread regarding new routes- but my internal email from the management has written this a few days ago regarding the 4th plane coming from STN to SEN:
"From 17 June 2013 we will move one aircraft from Stansted to Southend. This will enable us to fly to new destinations from Southend, such as Berlin and Krakow, as well as increase frequency on a number of routes."
Hopefully that will answer your question!?