Update: Apple has just announced that iPhone OS 4.0 (which has been renamed to iOS 4) will be launched on June 21. Click here for details.
Earlier today Apple [AAPL] announced iPhone OS 4. In the presentation they said the iPhone OS 4.0 release date was to be summer while the Apple iPad will get it in the fall, a few months later.
Reasons for the iPad delay are still unknown although we suspect they are tweaking iPhone OS 4.0 for the iPad to work things a little differently such as how the multitasking tray works.
With Apple only specifying summer as the iPhone OS 4.0 release date, that obviously puts it somewhere in June, July or August. We currently believe that the next gen iPhone (aka iPhone 4G or iPhone HD) is going to be announced early in summer, so we suspect that the iPhone OS 4.0 will be released along with the next gen iPhone.
Of course many people will be waiting for the update and an exact date, but unfortunately we just don't know it yet. However, as soon as we do find out we'll post an update to keep you in the loop.