I just finished the main game, so now I'm doing the extra stuff at the end <3 (SPOILER)I'm loving the alternate chapter. "Must... resist... urge... to be emo..." and the whole Who-Gets-To-Be-Pink thing are sooooo much win~! Though, I was a little sad not to see an entire picture of Shiki as she looks in the RG ):

I don't really see a sequel coming from this. The ending seems pretty final to me.