When I first read it, I pronounce it as as "key-on". However, there is something that concerns me in terms of quality for the show:
As we all know, all the characters in the TLK have names that have a meaning or significance in Swahili. (Mufasa doesn't have a translation, but it was the name of a real life Swahili speaking king). I quickly looked up what "Kion" might be, and the results show up...
...a complete blank. As far as I can tell, Kion doesn't have any historical or cultural significance in African culture, nor does it translate into anything in either Swahili not Zulu.
This might seem like pure nitpicking, and most likely is, but I have a serious feeling of worry. After all, even Kopa means "heart", and he is not a canon character (as many of you pointed out). The author of a few story books put enough effort to make sure that Kopa's name means something (although it looks like there was an error in translation in Kopa's case: His name doesn't mean "heart" as much as "heart", one of the four suites in a deck of cards. Points for effort). However, Kion doesn't mean anything as far as I can tell, so if they did not bother to continuing that tradition, should we be worried? I hope not.