I'm sure you guys have all seen this on the front page by now.
http://x3.xbimmers.com/forums/showthread.php?t=419700
But the part that piqued my interest was the last paragraph:
"...they are in the process of evaluating an X3 35iS using the same engine from the relevant Z435iS and US only 335iS. And an X3M using the powerplant from the upcoming 1M."
This seems to indicate that the engine in the 1M will NOT be the N54.