LOL. I first heard of the news on Wikipedia and I was all like, "Damn these 12-year-olds making up impossible rumors" and undid the edit; 10 minutes later my brother told me this and I was like WHAT.
Yes, I don't think the withdrawal was permanent but after the shebang with Majotourbillon, the witches were all, "HAIL NO, we ain't beefin' with you human dudes long time." Also, the Queen stepped down in place of Hana, who has yet to grow up to rightfully claim her throne. If Doremi and the girls are 16, Hana would be 6 years old, but if you really think about it, she's matured a lot during Dokka~n! She's kept her memories and everything in tact, but I think the witches think Hana is best left as a baby to continue to let her magic powers grow properly. The quick speed-up to 11-years-old probably didn't give her enough room to develop since her magical crystals broke in the process and she had to take exams to gain her own again.
Since it's a light novel (read: it's gonna be a short story no matter how much you look into it) and there may be a huge plot event where Doremi may gain back her powers (judging by the teaser illustration), I don't think it'll focus on the slice-of-life bit, which was usually reserved for filler episodes.
I think a "16" anime would be slightly possible, but I'm leaning towards it not happening. I really don't see what Toei could do with the plot, especially since Precure is their pilot magical girl franchise. The most I can see them do is release like a 1 episode special or something... possibly direct-to-DVD or something.
Edit: No, nothing was said about another follow-up novel releasing.