Astros favored to take Game 6 by Vegas (and others) but just barely. If they lose Game 6 they will not be favored to win the Series. They MUST win Game 6.
http://www.vegasinsider.com/mlb/odds/las-vegas/
Dodgers MUST win Game 6 or there will be no Game 7. If Houston loses Game 6, the odds may be against them but they would still have a chance to win Game 7.