WSU's class of 2009 was about 50% 4 yr degree grads, and it increased to where my class is OVER 70% 4 yr degrees. Additionally, 4 have Master's degrees and 2 have PhDs.
I was fortunate enough to be accepted while only having a 2 year Associate's degree. I highly recommend applicants to pursue the 4 yr degree route and to make sure your pre-reqs support that goal. For example, the Calculus I took would not have crossed over easily to a 4 yr degree in some of the Biology & Chemistry degrees.
This is definitely the path that the competition is headed, so be wise in your class choices. You'll be glad you did!