There has been much speculation as to whether the pre-episode IV crawl is a new transfer from the original '77 theatrical cut or an edit of the laserdisc post-episode IV crawl. The consensus seems to have come round to it being a transfer direct from the original '77 movie. There's a whole thread about it somewhere in this section.

This consensus has, in turn, led to speculation that, if a new transfer of the '77 opening has been done, then perhaps a new transfer has been done for the whole thing? And that is a very exciting thought...