Ozzy struggled badly, vocally, during the last Sabbath tour, as the DVD clearly shows. He's been through multiple serious illnesses and injuries in the meantime, couldn't even perform with his own band. I wouldn't want to see him in his current state for free, never mind pay a fortune to see him get wheeled on stage for a brief cameo amidst an array of guest singers. Let's not forget that, according to the band themselves, Bill wasn't capable of holding a tune together when they were recording 13, 13 years ago. He's not going to have gotten any better in the meantime. This is going to be Iommi, Butler and Bordin, for the most part, with Ozzy and Bill rolled onstage for a brief appearance at the end. Sabbath are one of my all-time favourite bands, seeing them in this state will be depressing and morbid.