Credible rumors are already claiming 2GB of RAM (which I'd imagine would be exclusive to the iPad Air version of the processor [for context: the A7 in the current iPad Air was a faster and bigger chip than the one that was in the iPad mini and the iPhone 5s; therefore, as rumored, it's possible that the next iPad mini will have the same CPU as in the iPhone 6 and iPhone 6 Plus, while the iPad Air employs a variant that has potentially more RAM and at least a faster clock speed]).
They're also claiming TouchID support, as well as a gold color option. They claim it might be thinner (hence the mock-up posted months back), which would be possible by using different screen/glass technology than what is found in the current Air. The thinner element would also enable them to tweak the current design to more closely resemble the iPhone 6 family. (With any luck, this will lead to a redesign of the current iPad Air smart cover as it is a definite step down from the iPad smart cover that preceded it. Unfortunately, this likely wouldn't apply to my current iPad Air; though it's still desired so that they fix the smart cover product line so that it's not as annoying to use and ugly in color as it is now.)