The new iPad Mini retinas are in short supply, and expected to be that way for a while. It's going to be catch as catch can probably all the way through the holidays. I won't go into the many theories as to why this is, other than to say it's probably why Apple did not set off fireworks when the new Mini launched.
I don't know why the LTE thing got started for referring the new models, since as AQ_OC said, the iPad Minis have had LTE models since the first generation. First time I've seen rPad Mini. It's the iPad mini with Retinal Display, or iPad Mini Retina for short.
It's not that I care all that much what people call them, as long as we all know what we are talking about. That's a loosing battle lost too many times. But the rPad and LTE things are potentially confusing.