New articles emerged again regarding Hikki's return and this time with more info.
http://news.livedoor.com/article/detail/11040408/
I hope someone could help us translate this article in full, but based on my understanding, it states that Hikki is currently in London, working on the album with a target royalty income of almost 200 Million JPY and 300Million JPY for the tie ins. This article also states that even though Terazune denied the rumours of Hikki's comeback, several people from the music industry has already had the news and that the new song as well as the drama will start on April.