From PNC's website
Today we announced that PNC Bank, a member of The PNC Financial Services Group, Inc. (NYSE: PNC), has signed a definitive agreement to acquire RBC Bank (USA), the U.S. subsidiary of Royal Bank of Canada.
The transaction is expected to close in March 2012
Looks like there's going to be competition for the #5 spot between Capital One, US Bank and PNC. From AP via Yahoo:
PNC said that the transaction will bring its total to 2,870 branches and make it the fifth biggest among U.S. banks. RBC Bank (USA), based in Raleigh, N.C., has 424 branches and about $25 billion of assets.