It is very difficult to predict the future solar energy development in Japan. After the Fukushima accident the Japanese seemed to abandon nuclear energy and turn to solar and other renewables as replacement options. Since 2012, Japanese government also introduced feed-in-tariffs which forced electricity providers to buy power from renewable energy suppliers.
This opened the door for many large solar energy projects such as massive floating solar farm near Tokyo which should power approximately 5000 average Japanese homes in 2018.
However, the government support for solar energy seems to be waning in Japan and Tokyo's long-term's commitment to renewables looks seriously in doubt because government is looking to kickstart nuclear energy back in the mix even despite the public perception.