Someone in the audience actually questioned this same thing as well. The Hasbro people responded to say that the Hotshot toy was to be released about 6 months after Cheetor, so wouldn't be looking like an assortment of yellow.
They also mentioned that the characters chosen were ones that were most well known, or most reflected the identity of that particular series.
Cheetor and Hotshot are key identities for their respective series, hence their inclusion in the anniversary line.