Don't think anyone at LTN is afraid of competition and having a narrow runway, half width taxiways and I suspect a mere CAT 1 ILS does not bother easyjet, as they can easily divert to another London airport when Southend is out of limits.
Easyjet has just left Belfast City Airport with its restrictions so we will have to see how Southend does in the coming years and whether Stansted tries to get Easyjet back in force.