News Retracted 7andY replaced "the third season" with "special episode".
According to the caption of Manga Time Kirara Carat October issue, the third season of Hidamari Sketch was announced. However, there remains a possibility that the editors mistook the special episode for the third season. This news is yet to be confirmed.
Sylpheed said: Looks like I'll delay watching this series so that I can watch all of it in one run.
Don't bother, the series is aired in non-chronological order anyway. Unless you have a time line and don't mind stopping half way through each episode in order to follow it, you'll never see all the events in the order in which they occurred. That said