And obviously, no tax cut has ever been permanent!
They go down, and then they go up. - every congress can do as it pleases without an amendment.
I think you misunderstand the terminology in this case. Bush's tax cuts are scheduled to end next year. If they had been passed without that proviso then they would be considered permanent and would require an act of Congress to change the rate. As it is the rates will go back to what they were before and Congress has only to do what it does best - nothing. The rates will revert without any action.