It's caucus, so organization trumps polls. the service unions have endorsed Obama. Edwards is without money and organization. The question is, where do his votes go? His voter demographic is Clinton's, but the policy aligns with Obama. Whoever is Edwards' second choice wins out.
It does give him some hope, but I wouldn't trust these polls especially since there is no way to guage how Democrats will vote in the Nevada caucus. It's likely that turnout will be very low and that anyone can win.
My guess is that Edwards takes a conciliatory tone in the next debate and hopes for an Obama/Clinton catfight that would make him an attractive alternative to the bickering. He will probably have a line that mentions the current spat.
All of that being said, Edwards has almost no chance to win the whole thing. Even if he wins Nevada, Obama will win South Carolina and that will make Hillary the favorite on Super Tuesday. Obama needs to win both to really have the wind at his back, which is the only way to overcome Hillary's name recognition.
It's kind of like getting into the NFL playoffs. Hillary and Obama are roughly tied for the lead, but Hillary holds the tiebreaker because of her ethnicity and superior name recognition. Hillary just needs Obama to lose and she cliches a berth in the general election. Obama needs to win out and have Hillary lose to clinch the nomination. Edwards is three games back and needs a complete meltdown of both candidates to win.