foregone conclusion

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An end or a result regarded as inevitable.
• noun A conclusion formed in advance of argument or consideration.

from the GNU version of the Collaborative International Dictionary of English.

• noun An inevitable outcome; a certain result; a certainty.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A predictable or inevitable conclusion, or one made without any consideration.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an inevitable ending
• noun something that is certain