Someone mentioned it above and now I can't find it or I would of quoted the person, but I do really believe that this E3 for MS will be about re-branding the Xbox, almost like a re-launch. Will it be just a Xbox One Slim that is the catalyst for this re-launch or a Slim and a more powerful console combo that will do it?
I am pretty confident based on what I have been reading with Sony demanding games released as of September be Neo compatible that the Neo will be out this holiday, would be no other reason to have software that supports it mandated with a September date.
MS and in particular Phil was the first to openely talk about updated consoles, Sony has only had leaks, nothing official from Sony. Thus far there has been very little leaks from MS, but if you remember to the reveal of the 360 Slim, it was leak free other than an image that appeared 12 or so hours before the conference, so they have the ability to keep things close to the chest.
With Nintendo announcing NX in March of 2017 is there even more incentive for Sony and MS to launch updated hardware this holiday?