Bush will appoint someone who will speak nicely to the Senate, promise to investigate like crazy and not merely be an appendage of George W. Bush. The Senate will fall for his bullshit and will confirm him.
The House and Senate will breathe a collective sigh of relief and stop investigating anything related to the (now) former Attorney General on the basis that he is gone and it is all now academic. They may also drop all other investigations in the pollyanna belief that the new Attorney General is a "good guy" and will do all of the investigating that needs to be done.
Congress will feel horribly "betrayed" when it turns out that new Attorney General lied to them during the confirmation hearings, and that he is a mere appendage of George W. Bush after all.
Business as usual. Mark my words.