They're too slow to keep up with modern battle groups. As beautiful and powerful as they are, they just can't keep up any more. They also consume massive amounts of fuel. I believe that it is correct to say that their time has come.
Personally, I would like to see them replaced with fully modern, fully armored, nuclear powered battleships. Nowadays, ships fight each other with cruise missles. I like the idea of a ship that just shrugs them off. Kind of like "hey, did you hear something" when a few exocets bounce off the hull.
Actually the Iowa class battleships were designed to keep up with the fast carrier task forces. They can make 33 knots if needed. They are some of the fastest battleships ever built.