Oracle is recommending that customers, who have not already upgraded to PeopleTools 8.50, go ahead and move to Tools 8.51 instead. In keeping with the standard Tools adoption policy, the Campus Solutions development team has moved to the 8.51 Tools release internally, and encourages customers to do the same. For those customers who have already upgraded to Tools 8.50, you are encouraged to move to 8.51 as well, but there is no requirement to do so. The July 2011 requirement for Campus Solutions 9.0 continues to be Tools 8.50 or greater.
Oracle Doc ID 957203.1, which was the announcement about customers needing to move to Tools 8.5 by July 2011, has been updated with this new information.
The bottom line is... If you haven't started your tools upgrade, Tools 8.51 is the release you should be moving to.