A few things:
First of all, the "line of succession" just applies if the President AND the vice-president die or resign, but if anyone below the president dies or resigns, he gets to pick a new VP based on Congress' approval. As of right now, the succession after Cheney would be Speaker of the House Dennis Hastert, President Pro Tem Ted Stevens (nutjob, a scary thought), the Sec. of State Condi Rice.
Also, I believe this is how manslaughter works; if Cheney was negligent or broke the law in any way when he shot this dude, and he dies, it's involuntary manslaughter. I believe that all hunting accidents in any state result in negligence on the parts of the both the shooter and shooted. I mean, maybe we should be giving Cheney a break; he is an old man and he did shoot an even older man. But the fact that it was an "accident" doesn't negate the negligence of the matter, and I really hate to see the words "hunting" and "accident" together.
By the way, they were on a quail hunt on a private ranch in Corpus Christi. Basically, they all pile into a Land Rover, drive up to the "covey" where pen raised, wingless, quailtards (I'm paraphrasing the Daily Show now) are shot at from 3 feet away.
In any case, I saw Scarborough's already asking the hard-hitting pundit questions like "Will Cheney step down?!" Well, it's way early for that. But I think this story has the potential for a lot more embarrassment than what has already ensued.