There will be 2 more Twilight Saga movies coming out.
Part one of Breaking Dawn will come out this year. I would give a date but it has already changed opening dates since the information was originally released to the press.
Part two of Breaking Dawn will come out next year.
For now Breaking Dawn is the last in the Twilight series in book form. There are rumors that there will be more in the Twilight series but so far those rumors are unsubstatiated.