Nine of the council's thirteen members are co-sponsors -- two are gay themselves -- and mayor Adrian Fenty is a big supporter. The bill needs to be approved by Congress to be enacted, and with a strong Democratic majority, there's a very good chance that will happen.
The only possibility the bill could be rejected is if a Republican Member of Congress goes out on a limb and tries to block it. If that happens, Democrats would probably have the 60 votes it needs to pass -- but the process becomes a lot more tenuous.
Most observers are saying gay couples will be able to wed in DC by late January or early spring. The District already recognizes gay marriages performed by the states that sanction it: Vermont, Iowa, Connecticut and Massachusetts.