Earlier today I spotted some posters of Plants vs Zombies: Garden Warfare that at a glance look like a CoD parody promotion for a PvZ sequel, but more evidence suggests that it could be the real thing. In following the URL pattern of the PvZ: Adventure page I guessed the location of this locked page, which differs from their 404 error page -- what you get when you enter the other parody names. Another report by Polygon found that www.pvzgardenwarfare.com redirects to the main Popcap home page.
This banner located in West Hall suggests that whatever this is will be located at EA's booth, and we'll likely see something on Monday during the press conference. Rumors on NeoGAF suggest the game is "a shooter with destruction and construction elements." SuperAnnutation noted this months ago, but also points out that the same character models for the parody "Grass Effect" and "Dead Face" were used. Hmm.
If you're really crafty at guessing the names of game assets based on patterns there's probably more evidence uploaded here, likely using similar name-spacing and underscores.
Clever marketing or real game? Only CrazyDave knows for sure.