Taxydromos newspaper (link) reports that F/B Mirtidiotissa will take over the Volos/Sporades route February 14 and cover the route at least until somebody else (F/B Aqua Jewel?) takes over in mid to late March.
The newspaper mentioned that Hellenic Seaways F/B Express Skiathos will be on the Volos/Sporades line starting in June and went on to say that a Flying Cat (5?) will come on line before Easter to serve Volos/Sporades – Agios Konstantinos/Sporades, at least for the Easter period.
Today the Hellenic Seaways site (link) shows Flying Cat 4 starting the Thessaloniki/Sporades/Agios Konstantinos shuffle on the first of June.