@gaff: from my experience very few session guys get performance royalties. It's usually just a flat rate for the session. The main exception would be unionized groups like the orchestras that do film scores in CA.
i find it really weird that people are so quick to throw all their hopes onto this game. the idea caught a lot of peoples imaginations but there is no concrete idea of how you actually interact with this game or if it is in any way interesting beyond the incredibly interesting premise. i also feel like people, perhaps because of the fact that not much is known, are expecting wildly different things out of the game. like i think jeff said something about going to planets and annihilating everything.
if it just turns out to be procedurally generated pokemon snap where my only interaction with the creatures and worlds is viewing them/recording them in some log i have no interest.