Kinokuniya doesn't take pre-orders on magazines. So you wait till the shipment comes in, which is usually a week, and order your copy. So I order my copy today. And am told the shipment came in last week and was sold out same afternoon. Are re-ordering. Will send then. Will get it in two weeks. Am still faster than saiyuki_manga.
Volume 4 comes out July 25, info thanks to the Russian scanlation linked by grendelity.