They have been retiring the older Ticonderoga-class cruisers, but keep changing their minds on the replacement cruisers. The Burke-class destroyers are extremely capable platforms, but the cruisers have larger command-and-control capabilities for managing a surface combat group in a battle and larger missile magazines for air defense.
They are also running into problems (primarily financial in nature) with the replacements for the Perry-class frigates. With the proven capabilities of submarines in modern warfare (ie the South Korean corvette Cheonan and the Argentinian cruiser General Belgrano), escort vessels are vital in any conflict against a nation which has submarine capabilities, which is almost everyone in today's world. Without escorts, cargo ships, amphibs, and oil tankers would be sitting ducks for all of the pig boats out there.
We need a bigger fleet, period. We are rapidly wearing this one out. The pace of operations is too high per ship.