So I started collecting those in 2012 when they released first such coin (dragon) and have all of them. And now here is 2020 and the new high relief mouse is Lunar 3, new design, new packaging. Will they just leave Lunar 2 high relief with only 8 out of 12 signs?
I would expect so. There have been a number of sizes / designs that weren't completed across an entire Lunar series.
The 1oz coloured Series II proof coins seemed to have ended in 2019. So there will not be 12 coins / animals with Series II, only with Series III.