Games have long since giving you the option to save before loading to another disc, even when the power is still going. Prime example would happen to be an old PS1 game, Final Fantasy 7. Since that game and console have been out long before the GC was ever made, it would make sense that developers would do the same thing today. Another thought about this is they would give the option to save before swapping discs for multiple reasons. They could be that you have to turn off the console and turn it back on, which is unlikely, safety in case someone accidentally presses the power button or something goes wrong when trying to swap the disc, resulting in the console powering off or even freezing, or the most obvious reason is a user needs to stop playing because his parents want him to sit down and eat dinner with the family. He would need a place to save so that when he loads again, he won't be thrown all the way back to disc 1 and instead just end up at the beginning of disc 2.
Most likely developers would have thought of this and planned ahead to give the user the option to save before swapping discs, so that any faults are solely the result of user stupidity and thereby they can't get bad reviews of the game.
