The start time is 10 AM Pacific, and the link to the events and schedule is below. I’ll try to liveblog the keynote here, when it starts. Of course, you can discuss the rumours, events, and aftermath here.
Extremely likely that the new MacBook Pros will be shown, after stagnating on bare-minimum Haswell refreshes. Skylake is all but confirmed, but there’s been shells that seemingly have an OLED touch strip, like the 2nd generation X1 Carbon. More out there rumours include a trackpad that supports the Apple Pencil.
Mac OS X will likely be rebranded into “macOS” to fit the new scheme that’s shared with iOS, tvOS, and watchOS. Possibly the minor version number will become the major version number, at least for promotional purposes. (This is what Solaris did.) The next version of Mac OS X will be 12 or 10.12, and will feature Siri integration. Siri’s integration with Finder is hinted at from error messages on iOS devices.
Possibly a new version of iOS. Multiuser and dropping iPhone 4S devices seem likely