Percy Weasley: Dies, because he is a traitor, or because he tries to redeem himself, thus providing a poignant, ‘complex’ moment. Sacrifices himself for the family? Is the least favourite Weasley, providing an easy sacrifice.
Why he might live: Part of a redemption story - Percy sees the errors of his ways and rejoins the Weasleys.
Mr. Weasley: Dies - Because nice (bland) guys finish last. Is connected to several of the main characters. Death was foreshadowed in Book 5.
Lives - Because he’s nice, he’s a Weasley and he’s a father. Also could be part of bridging the gap between Muggles and wizards in the future or could finally become the new MoM?
Fred and George: Die - Extremely popular characters whose demise could have a really significant impact on readers. I guess one could live, and the other could die, to add to the angst but they are a unit. They also don’t mind putting themselves at risk and standing up for others.
Live - Because the new world will require laughs and WWW.
Bill Weasley: Dies - Well, he’s already been bitten, and ravaged so…
Lives - Because he’s already taken his share of the knocks.
Ginny Weasley: Gah. Only Weasley girl, under the ‘Chosen One’s’ protection. Also don’t think that her death will have as much impact as a more well-developed character’s would. Most likely, she’ll get injured and Harry will assume she has died and will go berserk, blah, blah. If she does die, Harry will find some highly improbable way to bring her back. Also, JK just lurves her.
Mrs. Weasley: Too annoying yet inconsequential to get killed off and will live to sniffle, and shriek for another day. With Hagrid gone, someone needs to get hysterical at the funerals.
Charlie Weasley: A Weasley may pass on and shatter the OBHWF dream, but I doubt it will be Charlie. He’s hardly in the book.
-Theory by Westerly
Others have some different ideas about who will die…
Ginny: At the end of HBP, Harry gives Ginny a Peter Parker-ish dismissal because he wants to protect her. If Ginny gets killed anyways, he’ll realize that it won’t make any difference whether he’s distanced himself from people or not, so he’ll be able to not feel guilty about receiving help from Hermione and Ron (which is good because Dumbledore has hinted that Harry should keep them in on things as much as possible).
Also, even though we’re supposed to be rooting for Harry and Ginny, we haven’t been given any particularly developed scenes where we can actually fall in love with Ginny at all. The lack of substance with the relationship might be because JKR wants to make it easier to kill her off.
The only thing that I think would make it difficult to kill off Ginny is that she’s the first girl born to a Weasley in a very long time, and it might be hard to ruin that.