If I were a betting man, I would guess at Budapest, Belgrade, Bucharest and/or Riga being future possibilities. I think Budapest is underserved by Ryanair at BRS and Riga was a popular route some years back. Having said that, who could have foreseen Kosice being the next name out of the hat so I'll keep my fingers crossed for Bosnian and Macedonian routes (from a purely selfish point of view!)