As adamgreer noted, the producers of Wicked have no interest in expensive Elphies. They prefer to hire cheap, dime a dozen ingenues who can hit the money note and get on the fork lift on time. Hiring a Tony winner, there would be stipulations and expenses up the wazoo. The producers prefer to ride the cheap actresses until they shred her voice and cast her aside like an orange that has been juiced.
Salonga won't get anywhere near the role. Plus, she'd end up skipping matinees or Sundays to save her voice. She would be great though.
"The sexual energy between the mother and son really concerns me!"-random woman behind me at Next to Normal
"I want to meet him after and bang him!"-random woman who exposed her breasts at Rock of Ages, referring to James Carpinello