Yes. It will be an excellent summer to holiday in Greece. Some of the predicted visitors may mistakenly stay away, potentially lowering holiday prices and increasing availability for the rest of us. June is particularly smart (as are May and September) because the temperature will be perfect and the islands uncrowded. If there is one certainty about Greece in 2015, it is this: millions of travellers will enjoy superb holidays there. Life goes on.
While the next few weeks and months are likely to be tumultuous for the Greek people, the vast majority of tourists will be unaffected – just as they have since the crisis began. So I see no reason why you should cancel. Neither does the Foreign Office. Tellingly, consular staff have not changed the advice that prevailed last year, presumably because they believe the risks are unchanged. You can read the advice here: bit.ly/GreeceFCO. But to save you the trouble, it points out "There are regular strikes … sometimes called at short notice [that] can cause disruption to public transport in and out of Greece (including air travel and ports). Demonstrations take place regularly in central Athens, and have also taken place in other towns and cities." It adds "There is a general threat from terrorism and acts of political violence." (For comparison, that warning is milder than the prevailing advice for travellers to France and Turkey.)
If you decide to cancel you will lose some or all of the money you have paid – and you will deny yourselves a weekend that is likely to be full of interest, fun and romance. February is an excellent time to visit the Greek capital, to enjoy the monuments, museums and restaurants without the heat and crowds of summer.