Apparently someone got their hands on a draft of Thor and has revealed the potential opening. Of course scripts and drafts are changed all the time, so there is a chance this will not be the actual scene, but if you are still interested in reading it click on the button below.
Thanks to Iceman815 for the heads up!
The film opens up in the best possible way; the introduction of the Nine Realms by a 'booming voice' against a black screen. Embossed words describing each of the worlds begin to appear as the camera opens on the first.
The three Norse spirits Verðandi (present), Urðr (fate) and Skuld (future) narrate the creation of the realms and how the different manner of creatures in them came to be. First, the camera flies over Muspelheim followed by Hel and Niffleheim. The first character introduced Ymir, the first of the Frost Giants and his family in the realm of Jotunheim. You then pass over the realm of the dwarves, Svartalfheim, and the elves, Nidavellir. The camera flows through Midgard (Earth) and we see man exulting Odin in his temple. Finally, the camera pans through Bifrost, the Rainbow Bridge, to the the Hall of Asgard, which is filled with the Aesir. You see a glimpse of the Einherjar guard and winged Valkyries overhead, in what could only be Valhalla. Odin and Gaea are introduced while they are
. . . umm, conceiving a child. That child turns out to be Thor. Movie title appears.
The scene darkens and ends, when it opens again we are in 'present day' (centuries after the last scene). We find ourselves on the Asgardian border, where Thor (now an adult), his adoptive brother Loki, Fandral, Hogun, Volstagg and Balder (who is actually an older character, as apposed to the comics) are riding thunderously on their horses. They have been tasked on a mission to find Ivaldi, the Dwarf king of Svartalfheim. As they ride to the passageway between realms, we see a giant forge and three blacksmiths at work. They are creating the mighty Mjolnir, to present to Thor upon his arrival...