I am about to drop money on a Macbook.
Then its probably worth waiting, but "manage your expectations".
"No hardware - just OSX and iOS news" is a strong contender.
"Watch2" is a possibility - especially if it has new capabilities that they want to get developers writing for.
The MacBook Pro range is long overdue for a make-over - this is partly dependent on Intel releasing the correct chips (the specific mobile versions with the Iris Pro graphics have been slow to appear) - and if (as seems likely) they're introducing Thunderbolt 3 & USB-C there
may be a developer angle. That's the most likely Mac announcement but my gut feeling is don't hold your breath. If they
don't appear then its time to grab your popcorn and watch the fireworks on these forums. If they
do appear then it might mark the end of the 13" Air (obsolete in the face of a slightly thinner 13" rMBP).
The 12" MacBook was bumped a few months ago, so that's unlikely to change.
The iMacs were updated late last year, so they won't change.
The Mac Mini needs an update, but is often neglected so I wouldn't hold your breath. A new Mac Mini using Intel's
Skull Canyon platform would be brilliant, but I fear that is wishful thinking.
The Mac Pro needs an update. However, archaeologists studying a 2-million year old engraving hacked in the wall of a cave in the African Rift Valley have recently translated the ancient pictograms as saying "If Mac Pro not upgraded when next rains come, we getting black monolith from Moonwatcher. It full of stars!".