I have an iPad 2 and my niece sort of claimed it. The iPad Mini is basically an iPad 2 when it comes to hardware, right? iPad 4 is far superior, too heavy though.
The iPad Mini and the iPad 2 share the same processor and graphics architecture but it seems that the wireless controller is different. If Apple is going to make a Mini with a retina display then the processor (graphics processing) will need an upgrade. The big issue for Apple is most likely providing that power while still maintaining the claim of 10+ hours of battery life with the relatively tiny Mini battery. If anything holds Apple back from making the second-generation Mini with a retina display, that will probably be it.
That said, if you have a use for the Mini then go ahead and buy one now. Whether the new Mini has a retina display or not, it will be faster. That's a given with technology. I was holding out for a retina Mini but ended up buying a Mini last week because its usefulness for my business purposes was too good to pass up.
I have an iPhone 4S and an iPad 3, so I'm accustomed to retina displays. I will say that the Mini's lack of retina
is noticeable, but it doesn't bother me as much as I had thought that it would. By comparison, the lack of retina on an iPad 2 is very noticeable to me, but this makes sense: the pixel density on the Mini is higher than on the iPad 2 (163 pixels per inch vs. 132; the retina iPads have 264). It is "bad enough" that I'm strongly considering selling my Mini and purchasing a second-generation Mini if the second-gen has a retina display, even though I usually hold on to my devices and use them until they break. Yet it's decent enough that I'll need to go in to an Apple store to see the retina display for myself, and determine whether the difference is truly as great as I think it will be.
The buying advice is pretty standard though: if you can wait, then wait, because we're only a few months away from the release of the new Mini. Even if it wouldn't be available in Brazil for a few months after, the new release would help to drive prices down, right? Alternately, if you need the device now and/or could make very good use of it right now, then buy what's currently available. The new Mini will be better than the current Mini, but that doesn't mean that the current Mini will become functionless or unusable! Retina issues aside, it's a very decent performer (although I should note that I don't use it for games; gamers should probably hold out for the update).