Starting off I would like to say that this is just a light-hearted theory of what I believe could be the next league of legends champion. Through some investigation, through the shared link, I have discovered that that champion will be colorful [through the picture, I also gathered it being connect to flowers.] But with that being shown, this is what I came up with being what I was given through the video and along with my theory + theory for lore.
I tried to research this flower and came up with an almost exact approach of a Bellflower. Bellflowers are symbolism for everlasting love, affection, and consistency. What might we take of this and relate it to BOTH AHRI AND THE COLORFUL CHAMPION is that Ahri could have taken a very special version of this Bellflower, which caused her to get a charm ability and give herself beauty. Yet, in return, she realizes that every man could be evil and only want a sex drive [I related this to orchids, which are similar, and she could have taken a serum of a surplus of flowers]. Continuing, she could have reached this flower [or been handed this flower from this "colorful mage". The mage could be someone that likely has a lot of CC [support / mage / assassin] and actually might be able to shapeshift [if looking into serums to extremity]. This mage could have an ability that, when used on creeps, turns them into allies. However, when used on enemy champions could be a simple charm [or temporarily turning that champion against its allies]. I personally do not believe this champion to have roots or anything like Zyra, but I do speculate that it will involve a serum / charming system involved. After reading about the "Pure Vastaya" passage [and definition] it could be consulted that they might be bitter themselves upon drinking a serum that turned them into such a chimera. Or that since it says "pure Vastaya" that it was the original and wants to change other humans into this said form as well [And perhaps to not be alone.]