There was a report early last year that they had swung a deal with a solar company to look into building photovoltaics into the screens of phones, but could do it in such a way that the user wouldn't notice. It couldn't provide enough energy to allow it to be fully powered by solar, but it could lengthen usage. If it's coupled with a 3400 mAH battery, as rumored, then the phone could last a very long time.
Recent reports have indicated it may come out in March with a 25-30MP camera, higher res display, Snapdragon 805, 3GB of RAM, 32GB of storage, and MicroSD. That'd be a pretty killer phone. I'd guess that it would be a 8.1 launch phone. I have a feeling we will get several new phones of Microsoft (Nokia), HTC, and Samsung with a surprise or two thrown in when 8.1 launches - but that's just a guess.