As a non-fan of Chima, I was not aware the end was imminent.
It does appear to me the sets are unique and high-quality designs for the most part. I find the show marginally more interesting than Ninjago when watching with my son. I think the two themes suffer from the same issues, namely that no AFOLs are interested, and kids are fickle, always ready to move on to the next thing with little to no loyalty in general (OK that goes for adults these days too, but bear with me...)
Is the CHI Temple the most iconic set thus far? From my limited knowledge I would say yes, and agree that Cragger's Command Ship vies for a somewhat distant second. I have no idea if this new fire / ice sub-theme is popular or not.
The additional disadvantage for Chima is that, in terms of "investing" it is basically Ninjago 2.0, so not catching anyone by surprise (ala Ice Dragon sets and the like).
For these reasons I feel any long-term position on the theme would be super-risky, and agree that smart money dumps almost all of it next holiday season. I have passed on 50% deals constantly, and often wondered if I was making a mistake. I finally got over it by realizing I would rather wonder that and possibly regret it, than have them sitting in the closet, wondering if I made THAT mistake, and possibly regretting THAT decision.
That said, I have about 4 Chi Temples and a handful of ~85% discount finds that will make me some money in 8 more months.
If you go long and deep on Chima and win, you will definitely get a lot of attention for it. Good luck!