A new single has been announced by Sony for October 15, 2014.
I think it will be a ballad in the same kind of Sayonara & Always.
Kana Nishino ~ Darling ~ Preview of the Music Video
Kana Nishino in Seventeen Magazine, May 2011 ~
Kana Nishino in VIVI Magazine, September 2014 ~
Darling & Kimitte & Music Station SP (2014.07.25)