You kinda hit the nail on the head, in an inadvertent manner. Two things (feel free to correct or dispute me as I am going on memory)
Yeah pretty much what I was talking about, it makes sense for Audi to step aside in LMP1 since Porsche is currently doing better, and the same holds true in reverse in GT racing where Audi has a great car while the Porsche's getting outdated ( ironically making it a great GT AM drive. =) )
Edit: Still, it's a shame. The GTs already steal the show at Le Mans and this year about the only really interesting thing to happen with the LMP1s was that Toyota has the worst luck.