I have just read a interview with VIXEN in the German METAL HEART and they say they will open for Bon Jovi in Rio and they hope that the guys will come on stage to sing with them.
They seemd quite sure about the concert as the interviewer asked them about their future plans.

Are Bon Jovi going to play ROCK IN RIO? I think that's plausible. Doesn't it always take place in May? So it would be right after the release of Lost Highways and they announced anyway that they were going to play some festivals.