It looks like the developers are making some changes in the back-end to help players continue to prepare for Legion’s launch. Wowpedia has confirmed that items which drop from Demon Invasion chests now have a chance to be Warforged, adding at least an additional 10 levels to their existing 700 item level.
This reflects upon the development team’s earlier statement that, as the invasion proceeds and the Legion gets stronger, the loot will also get incrementally better to help hold the demons off.
There hasn’t been any word yet on how high the item levels will go but there are only two weeks until the launch of the expansion so depending on the final numbers we may see them go up fairly quickly.
Update: Items have the chance to roll an upgrade 720 item level as confirmed here.