The cast sounds pretty set in stone to me.
From a Playbill.com Interview with Marc:
Marc Shaiman: "It will be the first workshop — hopefully, the final one, too. We've had readings, but we've never had this. This has been a long-gestating project, mainly because everyone has been so busy with other things that we haven't had the chance to all be in the same room. Usually, I'm the one that everyone's yelling at. But, my God: Terrence McNally [who wrote the book to Catch Me If You Can] has written 3,000 plays in the last two years; Jack O'Brien and Jerry Mitchell have directed Stoppard trilogies and huge new Broadway musicals. It's been incredible."
Playbill.com: "And your stars, Nathan Lane and Christian Borle, have been busy, too. Whose idea was Borle?"
Marc Shaiman: "We had the auditions. He came in. Jerry was very high on him. Others came in, but Christian was so adorable and sings his ass off. His essence is just so — you can imagine him conning people by way of his good nature and sweetness. We were just completely charmed and blown away."
PLAYBILL.COM'S BRIEF ENCOUNTER With Marc Shaiman
"Winning a Tony this year is like winning Best Attendance in third grade: no one will care but the winner and their mom."
-Kad
"I have also met him in person, and I find him to be quite funny actually. Arrogant and often misinformed, but still funny."
-bjh2114 (on Michael Riedel)