STN-ALC 12 weekly will end on 16th June. Can't imagine EZY will end a route like that before the high (summer) season starts without a replacement (SEN-ALC).
So I think SEN-ALC will also see some additional flights (maybe double daily from current 6 weekly) + SEN-SXF 6 weekly + SEN-KRK 4 weekly + maybe some new flights to BCN (cause STN-BCN will be canceled too) and a 4th aircraft is required.