the only way i could see there being a event is if they talk about more then just the mac but unfortunately there are no other products to be released this year and the software updates are all minor enough that there really isn't anything worth mentioning to the public that we already know.
They can still briefly mention the AirPods that are going on sale around the same time as the new Mac products. And the Nike Apple Watches. They don't really need a lot of filler for a short event anyway if they refresh everything that needs refreshing in the Mac line. They have more than enough to talk about to easily fill about 45 minutes to an hour.
I'm convinced there will be an event with invites going out in the next day or two.