http://9to5mac.com/2011/07/11/new-mac-pros-and-macbook-airs-to-launch-this-week-with-os-x-lion/
"Surprisingly, it also looks like new Mac Pros are coming as early as this week. The new line was rumored to be launching in the last week of July or the first week of August, but it looks like Apple is getting them out earlier (or we just got the part numbers super early, which is unlikely). The new Mac Pros are may feature a re-designed enclosure that is both narrower and rack-mountable. A faster, 16 core model is also a possibility and Thunderbolt is an obvious addition. As expected, a new Mac Pro Server model will also debut...."
"Surprisingly, it also looks like new Mac Pros are coming as early as this week. The new line was rumored to be launching in the last week of July or the first week of August, but it looks like Apple is getting them out earlier (or we just got the part numbers super early, which is unlikely). The new Mac Pros are may feature a re-designed enclosure that is both narrower and rack-mountable. A faster, 16 core model is also a possibility and Thunderbolt is an obvious addition. As expected, a new Mac Pro Server model will also debut...."