The story will have Earth as the setting.
Episode 2 of the OVA, "The Red Comet" will be released in Fall. The biggest selling point is of course Unicorn Gundam vs Sinanju. Banagher Links will be fighting in normal suit and Unicorn Gundam will use its Beam Magnum. There will be many MSs and battleships from the U.C. era to see as well.
Some images of Episode 2's storyboard can be seen in this previous posting.
There's also explicit mentioning in the text shown in the image that the OVA will be moving at the pace of 2 releases a year. This is the first time we get to confirm on the timing I believe. With that in mind, Episode 4 will be released some time in the second half of 2011 then.
Image and information is from CyberGundam.