How much of the growth in development team sizes is a result of scheduling pressure from publishers?
Just because four people can accomplish the same work in half the time as two people doesn't mean putting four people on the job is the most efficient use of human resources. Accepting just two people means accepting slower production, but those other two folks can be applied to a different game.
Would publishers be better served by producing more games at a slower rate?
Bear in mind, this doesn't necessarily mean a barren publishing schedule. If average production takes four years instead of two, the publisher can still rely on regular releases by offsetting the various studios (Studio A's game releases in Spring 2010, Studio B's in Fall 2010, Studio C's in Spring 2011, etc).