UPDATE: As a couple of readers have mentioned, there is no such date as June 31st, 2012 so unless as a part of Topps exclusive contract with MLB they can now also create new days, they will need to fix that. I've sent a twitter message to @toppscards on Twitter to let them know as well.
I'm not exactly sure how new this information is but it looks like the time available to redeem codes and make trades on the Topps Diamond Giveaway has changed slightly. Along the left side of the site we have this message:
Thank you for your support to date unlocking codes and enjoying the Diamond Giveaway. The original plan communicated was to run the Diamond Giveaway until 1/31/2012 and then transition into our 2012 promotion, the site will now run until 6/31 but please note Diamond Giveaway codes in Topps Baseball Series 1 and Topps Update will expire on 1/31/2012 as stated and printed on cards, codes in 2011 Topps Baseball 2 will be the only cards active until 6/31/2012, all trading and shipping cards will be open to all until 6/31/2012. On June 31, 2012 at 11:59 pm The Topps Diamond Giveaway will be shut down. You must take delivery of your cards on or before this date.I don't really understand the logic that Series 2 codes will continue to work while the Update cards won't but, nonetheless, you will have six more months to trade and expand/improve your collection on the Diamond Giveaway site.