From the @PlantsvsZombies Twitter account:
Plants vs. Zombies 2, originally slated for a July 18th release, will now be released later in the summer. Stay tuned for more details.
The account later said the release was delayed because EA wanted to "make sure the game lives up to fans' expectations."
The game, officially titled Plants vs. Zombies 2: It's About Time, features the same lane defense gameplay that made the original a hit, but it includes time travel to all new locations.
The original Plants vs. Zombies game for both the iPhone and the iPad can be downloaded from the App Store for $0.99.