Preview at WWDC likely in June, followed by September launch.
Possible ‘iPad Mini’ Spotted in iOS App Developer Logs
The new identifiers found were "iPad2,5" and "iPad2,6". As Arment notes, the iPad2,1 through iPad 2,3 designations are known to represent the iPad 2's WiFi, GSM and CDMA models. The iPad2,4 represents a die-shrunk/cheaper version of the iPad 2 that was released alongside the 3rd generation iPad. Finally, the 3rd Generation iPad carries a designation of iPad3,x.
iPad Mini mockup (left) by iMore
As for "iPad2,5" and "iPad2,6", they have not been seen before, but Arment concludes they are likely to be the long rumored 'iPad mini' which is based on iPad 2 hardware.
The much more likely explanation is that iPad2,5 and iPad2,6 are the new “iPad Mini” in Wi-Fi and GSM, and I haven’t recorded the likely iPad2,7 CDMA version yet.By "Gruber Display", Arment refers to John Gruber's speculation that a iPad Mini made sense as a 7.85" display that shares the same resolution as the original iPad (1024x768). Arment goes into a little further depth in his blog post about his speculation on the internals of the iPad mini.
If so, this suggests that the iPad Mini is, effectively, an iPad 2: an A5 with 512 MB of RAM and enough GPU power to drive the Gruber Display, but not a Retina Display.
It’s a textbook Tim Cook supply-chain move: selling the last generation’s hardware at a lower price point to expand marketshare.
Apple is believed to be launching a smaller 7.85" iPad in the coming months. Rumors have suggested we'll see it launched as early as October.