Personally, I really don't think that JK even wanted a part in making it, I feel as if she's probably just bored and wants to go home, but all the publicity/money hounds just want her to cash in on the franchise even more so that they can get their measly 1.5 percent or whatever.
She basically wanted the series to END, and nobody is letting it die. It's like, when some douchebag makes a topic about something, and the creator of that something tries to get the douchebag to lock the topic, and they won't.
In brief, I don't really feel as if there was any reason for Pottermore.