Apple Insider is reporting that Apple will release a Retina iPad Mini in the second half of this year followed by a refresh in the first quarter of 2014 featuring a stronger processor:

"NPD DisplaySearch analyst Richard Shim is now saying that Apple will release two Retina iPad mini versions, "One in the second half of this year, then one in Q1 of 2014. The Q1 device will have a Retina display plus an updated processor." The move would be much like last year's debut of the slightly tweaked fourth-generation iPad, which hit store shelves roughly six months after the third-generation model."

(Via: Apple Insider)