I think I can safely say that McCain is going to lose this election. The real question is this: Who will come to embody the soul of the Republican party while they're essentially a non-entity in government?
I think we can divide the choice into two categories:
The True Believer: Someone like Sarah Palin. Charismatic, outgoing, extremely popular with the Republican base, but completely insane. This would be best for those who want the Republican party to die like some vestigial limb. Sarah Palin in particular will only be a fading star insofar as she remains in the spotlight.
The Practical Operator: Someone like Newt Gingrich. Although he has his own views, completely willing to project a public image of a centrist with bare Republican leanings. If McCain had run a less vicious campaign, I could imagine him falling into this position. This is the position that will rebuild the party, and the sooner they adopt it, the quicker they'll come back into the majority.
I don't think there's any realistic chance of getting a new party to replace the Republicans, like the Whigs in the 1800's. There are simply two many laws that embed the Republican/Democratic system into our political structure. A third party today has an essentially impossible task.