Obvious Andboy.
It happened with the iPhone 5.
Umad?
The iPhone 5 wasn't rocking 2048x1536 resolution display.
In fact it's display is actually less pixels than the current iPad mini.
iPhone 5 = 1136 x 640 pixels (727040 pixels)
iPad mini = 1024 x 768 (786432 pixels)
Therefore the iPhone 5 wasn't driving anywhere near the iPad retina resolution or required neither the GPU power or larger battery in order to deliver that resolution.
The iPad retina has a 42 watt battery resulting in a 9-10 hour battery life
The iPad mini currently has a 15 watt battery
If the iPad mini was to get the guts required to drive a retina display at this current time (there has been no new chip released offering significant power savings but still delivering performance of the A6X ) then the resulting hit in battery life would be astronomical. Never mind making the device thinner.
The previous retina iPads were actually thicker than the iPad 2, to accommodate the hardware / battery differential.
Can you see apple grafting in current A6X or previous A5X into an iPad mini , resulting in a 3-4 hour battery life in a 15 Watt battery ? No - of course not.
AU Optronics who are producing the retina displays will not have a mini display until Q3 2013 with large scale production for Q4 2013
We can assume Apple will then need the revised A7 chip which one assumes will be faster and deliver better GPU power without requiring exponentially more power to drive it, resulting in a chip powerful enough to drive a retina display without significantly reducing battery life or requiring a much larger battery in the mini (which would result in a thicker and heavier mini).
If Apple chooses to update the Mini in march it will be for an A6 without retina, and given how well the current iPad mini is selling it really begs the question why would they bother given the current hardware is not impacting on sales, so why re-manufacturer something that they are struggling to keep on top of demand for?
Personally and practicality wise I can only foresee the mini being updated in Fall 2013 with retina display.
The matket analysts that seemingly come out with these predictions do so based on history of release dates and 'market expectations' and not based fact or current technology limitations and predicted release dates for technology required to actually deliver the product they are predicting the release date for. It's a flawed viewpoint, but one that continuously stirs up the hornets nest, which is exactly what the Markets want irrespective of what actually comes to pass.