I think it is logical that Zelda is needed to revive the Master.
Ghirahim has a goal which is to revive his master. If he didn't need Zelda to do that, he would not chase after her.
Also, the fact that Link dreamt about this Giant Worm, must mean that this Giant Worm is very important to the story.
It doesn't HAVE to mean that this Worm is the Master. He could as well be another important figure or perhaps Ghirahims transformation forme or another important villians transformation.
However, in the intro movie, it is said that the "evil rise from the earth" or something like that. The worm in Links dream, is also seen to rise from the earth; the EARTH SPLITS OPEN and then the Giant Worm comes out of that hole.
You can see this in the first 25 seconds of this video:
http://www.zeldainformer.com/2011/1...-in-hd-new-play-through-with-new-content.html
Based on this there is considerable proof that this monster will indeed be the "evil that rise from the earth" and thus Ghirahims Master.
What I am afraid of, is that this monster will indeed be the final boss, while he probably has:
- NO character development
- NO specific personality
- appears at the end of the game
= just a random beast with no personality or character development at all that appears at the end of the game to fulfill the role of 'standard evil monster rawwrrr! ' and be the final boss.
I hope Ghirahim (or another developed character) does a 'Kefka' on him and overthrows his Master, steals his powers and takes his place..... rawwrrrr...
EDIT
Thinking about it, isn't it just too idiotic?
You start the game:
The first thing you see is, ofcourse, the intro movie and after that those first 15 minutes begin.
So you first see an intro movie in which it is stated that a "evil rise from the earth" and not even three minutes later a cutscene is shown in which the earth splits open and a evil looking monster comes out of that hole. I can imagine even a 10 year old infant seeing that scene and thinking "so that is evil monster Link has to defeat hihihi".
Doesn't Nintendo realize this is just too obvious or are they misleading the player?