Just a little info:
On my outbound flight, 3 days prior departure "I" became available (thx expertflyer). Although I was waitlisted, I had to call aegean for the upgrade process (didn't happen automatically for me).
On my inbound flight, business class was fully booked (12 pax) already 4 days before departure and only 8 seats remained buyable in economy. Was silently hoping they'll open up a business class row to get the upgrade! But no business class seat has been made available for selling (and no "I" opened up in parallel) until checkin closed. There were 7 empty seats in economy during the flight.