So I emailed someone that works with transportation at ASU, and here's what I got:

"The current student U-Pass is good until June 30, 2009, so up until this
point it will continue to be free.  What happens after this date, I do
not know and have not heard any discussions concerning that matter.
However, you are correct that employees of the university do have to
pay, but it's still at over a 50% reduction than normal costs from
Valley Metro."

So hopefully the U-Pass will be free for a while! It's a definite money-saver for students.