It could be, although I wouldn't bet any money that Win8-ARM will be able to take a program in IDL format, compile it, and run it; I'd wager you'll have to go back to the original source file in C# or VB.net or whatever and generate a new IDL.
In fact, I seem to recall that they won't be supporting the old Win32 API on the ARM implementation at all -- only the new "Metro" API. But I could be wrong about that...
---Joel