I couldn't see anything regarding the blue essence emporium in the recent patch notes, so I did a little digging and it seems that the blue essence emporium will go live from the 13th of December 9pm PT until the 27th of December 9pm PT.
You can read more here.
External link →Wait /u/RiotMeddler said in the dev blog video that we would get mistery icons (not the mini) and the mistery wards back since there weren't in this summer Emporium. What happened?
Following up with folks to find out (hoping it's just that we didn't put that stuff in the FAQ, not sure yet though)
devtrackers.gg