KittyxthexKitsune
I was told that they haven't released any information other than Kentaro Yabuki is starting a new series in January.It may not even be a Black Cat sequel,so don't get too excited,but I think it's likely.It would be wise not to get your hopes up too high like me,though.
before starting To-LOVE-Ru and shortly after Black Cat ended Kentaro Yabuki made a statement that he wanted to create a new series in the same world as Black Cat, not really a sequel, more of a spinoff, but that it would also be used as a way for popular Black Cat characters to show up and to tie up the few loose ends left in Black Cat. it really wouldn't be a true sequel even if he went with that plan, but if he does really want to work on it then there's a chance that'll be his next project.
personally I'm hoping for either that or more of (or a new version of) Yamato Gensouki, his first real series (which was only two volumes long and left unfinished).