An A6 on a Retina Mini would bring per-pixel performance that's equivalent to an iPad 3. As an owner of an iPad 3 running iOS 7, I can tell you that is absolutely unacceptable, and I'd be floored if Apple management thinks differently and releases a new product based on that.
The answer then is either an A6X or an A7 for the rMini, with the A7 being the obvious choice, as it has a more die efficient GPU design and is already benefitting from the iPhone 5s's manufactory ramp.
I agree an A6 isn't going to be offered on a RiPad Mini. I think the processor is going to come down to one thing.
Will there be a A7X? If yes, I think the RiPad Mini gets an A6X. If no, then it gets an A7 along with the iPad 5.
I've talked about it before, but I strongly believe the $329 price point of the original iPad Mini was to mark Apple's "spot" on the pricing tier for the iPad Mini in general.Edit: There's recently been a lot of blog posts and articles from the chattering class regarding possible price points. Building off of that, I'm going to guess $299 A6 vanilla Mini, $399 A7 retina Mini, $499 A7X full-sized iPad. Also, if the leaks showing the full-size iPad's volume reduction are indicative of the final weight (I'm betting on <1.2lb but hoping it's close to 1.1lb/500g), the product's achilles heel might be "solved".
A RiPad Mini will be $329. The old iPad Mini will be $229.