The description just makes it sound like an extra regular issue, so maybe it is extra long or has some extra mini-stories or info in it like the old Annuals (it doesn't sound as good as the old Annuals though). Not sure what the point is, if it is just an extra "issue" in a month. Maybe they have so much story to tell, it needs the extra "one-shot" issue.
It has Metroplex on the main cover, and deals with story of the Cybertronian Knights. There will also be an incentive cover too.