Karo used to be a guy I liked to watch. I think a fight with him when he was in his prime, and the GSP of the same era would have been an all time great(now, not so much). Id say the addition of Karo is more likely to add up to a few more on the fence customers buying the ppv, but if the difference in views/buys/whatever pays his salary, Id be suprised.
They did fight during Karo's prime. He was GSP's first UFC fight