I wouldn't bank on Virgin Atlantic returning to the London-Athens route, no matter how successful it was.
For the past 2 years they operated their only scheduled short-haul service with a sole A321 alongside the 4 A320/321 aircraft of Virgin Sun which operated charter flights, using Virgin Atlantic flightdeck crews.
Since Virgin Sun was subsequently sold to, and closed down by First Choice and Virgin as the name could no longer be used by the new owner, the viabiliy of the sole A321 and the Athens route was always in question.
With the events of September Virgin have retrenched to protect their core markets. The Athens service is definately outside their core markets, and is the sole remnant of a once planned short-haul network (remember Virgin CityJet?) Unless a wider programme of short-haul flights is introduced by Virgin Atlantic, then I believe that the Athens service is consigned to the history books alongside Virgin Sun and flights to Dublin and Maastricht.
With codeshares with bmi british midland, Virgin have for the past few years been concentrating on expanded long-haul service. Virgin knew they would have 4 surplus A320/321 aircraft last year when First Choice took over Virgin Sun, had they had the slightest interest in doing so, they could have used these aircraft to expand their short-haul service between any two EU cities, without restriction. They chose to return the aircraft to their lessors early, even before the events of September. That says a lot about Virgin's interest in the short haul market...