Google just set a date for some sort of announcement: Sept. 29. But it's not saying what it's for. (Hint: It's Android and Nexus.)
You will almost certainly be able to say "hey, what's up, hello" to a new Nexus device (or two). There may be a new Chromecast as well.
Judging from the "s'mores" reference, it's also going to include the release of the latest version of Android, which Google code-named "Marshmallow." The Android M developer's preview of the operating system debuted at this year's I/O conference back in May.