If it ever comes over I feel Sierra is a given, unless she is busy at the time, Ramin has tweeted that when le leaves the london show later he will not be donning the mask after he does the 25th anniversary concert, so there is a chance he may not be offered the role, but who knows, if it happens, Also, you would have to see what Equity deal may be made to get Ramin to come over, I believe he is Canadian so that may help.
It wont happen till 2013 earliest depending too on the availability of a nederlander theatre (unless they change and go to a shubert house) I'm not even sure what house will work well based on the Melbourne design. Yes the design may be altered, but from what I;ve seen, they would need a house with a lot of FOH space unless they will end up with a show with many partial view seats.
I feel it would 'look' good in the Palace or even maybe it can fit into the Lunt. Idealy it would 'look' best in the Broadway but that's not a Nederlander house. If Catch Me does not pick up they may very well end back at the Simon.
http://www.flickr.com/photos/27199361@N08/ Phantom at the Royal Empire Theatre