9to5mac, citing a "Mr. X" as their source, suggests that the new versions of both machines are slated for arrival sometime this week. The new models are expected to be sporting Lion, Apple's yet-to-be-released version of Mac OS X, which the company said would be ready to go this month. A gold master version of the software was delivered to developers on July 1.
On the MacBook Air side, there are four models listed with the new part numbers, matching up with Apple's four existing offerings on the 11- and 13-inch versions. For the Mac Pro, there are also four part numbers, which meshes with the existing quad-core, 8-core, 12-core, and server Mac Pro models.
In February, CNET reported that Apple was cooking up a refresh for the Air for June, a deadline that's come and gone. More recent reports, including one from Taipei-based DigiTimes claimed Apple was ramping up production to get units ready in time for a July launch. The new models are expected to include the Thunderbolt I/O port, alongside a processor bump to Intel's Sandy Bridge Core i series processors--two additions that have been made to Apple's MacBook Pro and iMac lines this year.
As for the Mac Pro refresh, which my colleague Brian Tong noted would be coming later this month, or in early August, there's been talk of Apple working on a brand-new enclosure. The current tower design has received a number of tweaks over the years, but remains a carryover from Apple's PowerPC days.
Not included in this batch of part number goodness is any mention of updated Mac Minis or MacBooks. Both product lines are about due for an update, and there's been mounting evidence on the supply side that the two will be getting just that.
Apple is rumored to be holding "overnights" at its retail stores Wednesday night, suggesting the company is setting aside time to ready its stores and employees for new products.
Update at 9:10 a.m. on July 13: 9to5mac has posted an update this morning, noting that what were believed to be part numbers for new Mac Pros are actually upgraded models of the MacBook and Mac Mini. The blog suggests that the new versions will contain Thunderbolt ports and "faster processors," as well.