I'm not certain that PC players would be satisfied with a port. I know that the primary reason I buy multi-plat games on PC is for better and more extensive graphical options moreso than just kb/m. I'm also not certain Bungie would be happy with porting for the sake of porting (could be wrong).
In any case everything they've said points to them not wanting to work on a PC version for simultaneous launch.
Also, I just remembered, did they say they already have an internal PC version? I believe there was even a thread about it.