I just wanted to point out before everyone started cumming in their jeans that it is very rare that any band is ever on a bill for either a package tour or a summer festival two years in a row. It is bad business, because the general majority of the people don't want to see the same line-up two years in a row. Sorry, but the only band from Gigantour '05 that will be on next years is Megadeth. Possibly Anthrax because they only played like 4 shows, so it's a slightly different situation.
Sorry to burst everyone's hopes and dreams, but it has little to do with them fitting it into their schedule or whether they are good enough to play first stage. It has to do with the fact that they just won't be there. Jim Sheppard from Nevermore said that they were asked back to Gigantour, but for '07 because they just don't do two years in a row. Anyone who allows a band on two years in a row is a retard.