Im not sure if there will be a significant upgrade to the M system.
If there was one however, the LCD technology is way beyond anyone on this forum. Camera can be thinner, more efficient and still retain the LCD. Heck they may even include a mechanical back LCD cover to offer a streamlined look. or make it an optional accessory for $699
I think the real announcement will be to the X system or the S system. A smaller, faster and more efficient version of S2 perhaps, much like the nikon D800E