Most likely because the stuff they're working on right now is large changes, engine merges, bug fixing and stuff like that. The concept art is just to rehash their main focus for the future updates.
EDIT: I don't see the similitarities, the last update mentioned bikes and new weapons and more bug fixing, this regarded soft skills, life span and aerial vehicles, and the new Military base.
Yeah, you're right. I caught this at the end of last week from twitchcon. My days and weeks are folding into just 'lapses of time'...Oh the joys of working from home.