Mikkie4, if they do actually add an additional departure point I'm sure it will be LCY which has no flights to the major cities and thus offers a USP for SK, which they have lost with the major incursion of DY in particular but also EZY/FR into their markets.
Failing that it will be STN with which SK has a long association and has lost service to CPH (as good as), ARN and OSL. The major airports offer the only possible weapon in the fight with FR.
As great as SEN is, I'd be extremely surprised if SK moved in.