Hi everyone it's Xebs, reported by Yahoo! Japan, singer Utada Hikaru (the artist who sung the Kingdom Hearts theme songs) may resume her music career in Spring 2016. Back in 2010, she announced that she would be going on hiatus for an undetermined period of time in pursuit of "human activities". During that time she found a new love, got married and had a baby boy in July of this year. She is currently working on her new album.
Also, it's currently unknown whether she will be returning to sing a new theme song for Kingdom Hearts III. (Fingers crossed).