Point of order: There is no P4 or G5, anymore. No conferences get auto bids. Only the top 5 conference winners. 98% of the time, all of what we all consider the "P4" will get those auto bids, with the "G5" getting one of them.
That being said, I think the G5 will always get at least one auto bid. Do you remember the old BCS? The old, old BCS? The original BCS rules stated that the G5 teams (they called them something different, back then) needed to be in the top 4 of the BCS standings in order to get an auto bid to one of the BCS bowl games. And there were only 4 BCS bowl games, counting the championship game. I believe that the G5 conferences threatened a lawsuit, so the P5 conferences opened a 5th bowl game (keeping the existing 4 BCS bowl games, and adding a championship game to the 4 bowl sites), and changed the criteria for G5 teams from top 4 to top 12.
I don't know who sues or gets sued, but the story we were fed back then (2005-ish) was that opening the gate to let more G5 teams in was started by threats of a lawsuit.
