Are you ready for an iPad with beefier memory? A new fourth-generation iPad with Retina display — and perhaps as much as 128 gigabytes of memory — is being readied for release, sources tell 9to5Mac. The upcoming slate would not be a new design but rather an addition to the current fourth-generation line, with the same color and wireless combinations as the iPad 4, these unnamed sources say. Pricing is unknown, but the new model is described as a “premium SKU” (stock keeping unity) that would join the current lineup of 16GB, 32GB, and 64GB iPads. A source at a large U.S. retailer provided 9to5Mac with what is purportedly a new SKU listing for iPads that includes a fourth model labeled as “Ultimate” to join its current lineup.