can the oil released in the gulf eventually contaminate our drinking water?

It's very unlikely this would ever happen. The oil won't evaporate and fall inland as rain so would never make it into rivers and lakes. Even if it did, it would be filtered out before getting to your home.

No, there is no way for th oil to get inland and contaminate our drinking water, rivers and streams flow into the gulf, the gulf doesnt flow inland so there is no way oil can go upstream

The oil is still leaking so it is possible the oil could seep into rivers and lakes. We haven't seen the end yet. Water systems in the Gulf States are potentially in the most danger.

Lew is right that water treatment would get out oil contaminants but would you want to drink that water - wondering if they got it all? Not me!

While it is possible, in theory, for oil to be washed upstream (google "tidal bore", if you are interested), drinking water intakes are all situated well above the area that might be reached, with the possible exception of the Amazon.