You really think so, Jack?  After all, LAM was in general release, not only at home but around the world.  Whereas, supposedly, the full AMBERSONS was previewed once then chopped up.  I even remember reading somewhere that the head of RKO personally ordered the excised Welles' footage burned. 
You're certainly more knowledgable on this subject than I, but from all I've read, I'd give LAM better odds than AMBERSONS of ever being seen again.  Though, frankly, we ain't gonna get either one.