Wonder if they are getting the runway ready in time for the rumoured Jet2 base expansion in 2020. There are rumours that BRS/CWL/SOU or even BOH could be used by Jet2 in 2020.
Could envisage a pretty good base for Jet2 at SOU given they don't serve LGW or LTN and have no intention to fly from LHR when the 3rd runway is open (unlike easyJet mentioned publicly).
If SEN can support Ryanair 737-800 operations to Corfu and Malaga then you can be sure that SOU will be on their radar also. I could imagine Ryanair wanting to serve Dublin & Belfast for a start at much higher frequencies than would be possible from BOH.