We’re now into the timeframe when Philae will be receiving enough sunlight to theoretically charge its batteries enough to communicate, even in its unfortunate resting position. The first opportunity, last Thursday, was met only with silence, but there are still opportunities through the next week. More opportunities will come in April, when additionally the comet will be warmer — but also more active, which makes things even more unpredictable since nobody really knows exactly what happens around a comet when it becomes more active.
Listening opportunities are governed by the geometry of Rosetta and the landing spot, circled in the image below from Rosetta’s OSIRIS instrument. As Rosetta’s orbit precesses around the comet’s nucleus, it becomes more or less able to get a clear line-of-sight to the lander’s radio equipment. So if we don’t hear from it now, there’s still a chance for later. The odds are slim, but cross your fingers anyway!