It has been recently reported by Digitimes that their electronics supplier-based contacts state that Apple is currently in the works of prototyping two versions of the third-generation iPad, or iPad 3. The site says the third-gen iPads have been codenamed J1 and J2, and based on code strings from 9 to 5 Mac, it's at least likely that the iPad codenamed J2 mentioned in the report may come with a Retina Display, as well as a dual LED-bar system to power the high-resolution display, which have already graced Apple's iPhone 4 and iPhone 4S models.
An excerpt from the article about the J1/J2 (as well as more device findings):
Since Apple demands that the new iPad model will need to be thinner than the iPad 2, while raising the machine’s screen resolution to 2048 by 1536, upstream component makers have been working aggressively to adjust the device’s LED and panel module designs to satisfy these demands, but the work has affected the launch schedule of the new tablet PC. Apple is currently giving two tablet PC projects codenamed J1 and J2 to its upstream partners for development. The sources revealed that the major differences of the new tablet PCs compared to the previous model are their size, specifications and technologies. Since the new tablet PCs have a higher resolution, Apple has demanded the design of the light source to be changed from a single LED light bar to two LED light bars on the left and right sides of the machine, but since the method of adopting two LED light bars has created difficulty in shrinking the machine’s thickness, some vendors have come out with designs that only adopt one light bar, but are packing two LED chips into one package. The sources pointed out that the J2 project seems to be an upgrade version of the J1 and although Apple has not yet decided which project will be used for the final launch, Apple is likely to make the final decision based on its needs. As for the upstream side, the component suppliers have already conducted pilot production and prepared for mass production.
The report essentially states that Apple hasn't made a decision between the J1 and J2 models, but it seems likely that the J2 model is actually the 3G model, and it's quite possible that there is indeed a J1, but it hasn't been found in the iOS 5 code yet. The J2 model of the iPad 3 having been uncovered in iOS 5 code means that the device is actually in testing right now against an iOS 5 software release.
In fact, according to 9 to 5 Mac, the J2 codename has been hovering around since the initial betas of iOS 5.0, and as you can see in the screenshot, there's an unknown T39 device also in stages of testing. We'll get back to you later about this whole situation when we have more concrete information, which should be in the very near future, since Apple's probably due for another new iPad launch soon.
[Digitimes via 9 to 5 Mac]