As the name implies, it looks like we will be traveling through time defending out strong holds from the zombie horde with our amazing and powerful plants. Also Crazy Dave will be there to sell us a few items and power-ups to make sure we don't get overwhelmed along the way.
Confirmed locations in time are Ancient Egypt, The Wild West, and some period where swashbuckling pirates were popular. To go with these locations will be new plants and zombies to fit the locale and most likely use the environment to their whims. There is no real news on what any of those will be, but I am sure that information won't be too far off.
Another interesting thing to note is that PvZ2 is going to be free to play. Normally this is a dreaded thing to me as it really means "free to play a little bit of the content but if you want the real game you have to pay." What is interesting here though is that ALL of the levels and creatures within are going to be available free to play and it will be the little extras and power ups that will cost you real money. If that makes it so I can still enjoy the entire game without complaining I don't want to spend real money on one little power up, then I am sold.
Like I said, there is sure to be more information coming in short order, most likely on Monday during EA's E3 media briefing. It kind of has to seeing as currently Plants Vs. Zombies 2: It's About Time is slated to hit all of our iOS machines on July 18th. Keep an eye out for it.