I'm going to be quite surprised if WWDC brings OS X Ive, iOS 10, Apple Music Beta 2 AND a full refresh of Macs. I've read "September" somewhere but I can't remember where (and I am not an insider either).
Last year's was nearly 2.5 hours. With new products to support, like Apple Watch, Music, iPad Pro, Apple TV, etc. events are going to get longer. There's a lot to talk about.