Since future is always uncertain, even with ""favorable conditions" (e.i. NY will win Los Astros at NY pitching CC) the key factor is how Casinos/betting shops/betting firms/betting web pages/etc. reward those odds. This is how they make tons of money. A bookie/gambler always is who makes the bet (try to predict the future), on the other hand betting houses put the conditions (reward), of course based on probabilities. There's the key.
If the odd-makers realize (after their analysis -- whatever it means--) that an event's probability is very low in order to happen, the reward is big (e.i. Los Astros will win the 2012 WS 100/1). On the other hand, if an event's probability is very high, the reward is symbolic (You need to bet tons of money in order to win something atractive)
Future odds are peculiar. Look at the Philli's line, they pay you 11/2. The reward is very attractive since this kind of bet is still a loooong shot because a lot of factors will be in effect next 8 months that could change the final result, but STILL, the Phillies are the most likely frontrunner in order to win the WS. TEX, LAA and NY are above us. According with odd-makers/experts they have better posibilities than us to win the ring, but still it is a loooong shot for each team.
So yes, future odds are a good thermometer in order to rate the strength of a team (question marks).