OK...going by the bio pages on WWE.com's Raw and Smackdown superstar sites respectively, I'm going to list all the WRESTLERS (not managers, announcers, authority figures, or valets) not going to be on WrestleMania this year...either by injury or something else.
First, from Raw:
Christopher Nowinski
Gail Kim
Ivory
Jacqueline
Jazz
Johnny Blaze/Spade (whatever it is)
Jon Heidenreich
Lance Storm
Lita
Mark Henry
Matt Hardy
Maven
Rico
Rodney Mack
Rosey
Scott Steiner
Spike Dudley
Steven Richards
Sylvan Grenier
Test
Trish Stratus
The Hurricane
Tommy Dreamer
Val Venis
William Regal
Now, the Smackdown Side:
A-Train
Billy Gunn
Chuck Palumbo
Edge
Hardcore Holly
Johnny Stamboli
Matt Morgan
Nidia
Orlando Jordan
Paul London
Rhyno
Sakoda
Sean O'Haire
Shaniqua (?)
And there you have it.