And for that matter dietcoke cherry vanilla.

i actually like the pepsi versions and seek them out when i am looking for a cold 20 oz. Is it inevitable that coke will come out with this if pepsi has success with it.

And for that matter is pepsi selling a lot of the cherry vanilla?

Coke did do a semi-Cherry Vanilla (It was called Black Cherry Vanilla) version a couple years back. That seemed to be a flop.
As for Cherry Vanilla Pepsi, I think its just a local thing but I have yet to see 20oz, but both varieties seem to sell well from what I've seen.