The iOS 6 beta 5 has found to contain reference to 128GB iOS devices which has been pointed out by @iNeal and iDownloadBlog.
The reference to a 128 GB capacity comes as part of SystemPartitionPadding key in the build manifest.
9to5Mac has also found the new iPad SKU in a US retailer database which has confirmed the pricing. The 128GB is reffered by "ULTIMATE" name which means it might be an addition model along with the current “GOOD,” “BETTER,” and “BEST,” which are 16GB, 32GB and 64GB models respectively.
The pricing is likely to be $799 for the Wi-Fi only model and $929 for the cellular + Wi-Fi model.
So a higher capacity iPad is almost certain, there is also a possibility that the iPhone and iPod may also come in higher storage capacities.
Source 1 | Source 2
The reference to a 128 GB capacity comes as part of SystemPartitionPadding key in the build manifest.
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9to5Mac has also found the new iPad SKU in a US retailer database which has confirmed the pricing. The 128GB is reffered by "ULTIMATE" name which means it might be an addition model along with the current “GOOD,” “BETTER,” and “BEST,” which are 16GB, 32GB and 64GB models respectively.

The pricing is likely to be $799 for the Wi-Fi only model and $929 for the cellular + Wi-Fi model.
So a higher capacity iPad is almost certain, there is also a possibility that the iPhone and iPod may also come in higher storage capacities.
Source 1 | Source 2