Why wait for the USS Barack Obama ? Seven out of the ten Nimitz class carriers are named after former US presidents, one is named after a admiral, one after a congressman and one a senator. And the first 2 Gerald Ford class carriers are named after former presidents.
It is not inappropriate to name capitol vessels for historical figures...those universally recognized as having contributed to the preservation of the nation, particularly in times of major conflict or war.
Let's look at the vessels you cite:
CVN-68 Nimitz - Overall commanding Admiral during World War II naval combat in the Pacific
CVN-69 Eisenhower - Overall commander of US Forces in World War II and later President
CVN-70 Vinson - Served over 50 years (1914-1965) in the US Congress, was very influential with Military matters through two world wars, and particularly US Navy matters, and was known as the father of the Two-Ocean Navy.
CVN-71 Theodore Roosevelt - Combat veteran, major contributor to and influencer of US Navy, and ultimately President.
CVN-72 Abraham Lincoln - President who led the nation through the civil war and preserved the Repuiblic
CVN-73 George Washington- Father of the nation and commanding general of all US forces in the Revolutionary War.
CVN-74 USS John C. Stennis A very ranking Senator who chaired the Armed Services Committee for years and who was extrremely influential in the development of the modern U.S. Navy.
CVN-75 Truman - Combat officer in World War I, became President of the United States who was victorious over Japan.
CVN-76 Ronald Reagan - President of the United States who engineered and preservered in winning the Cold War and was a huge proponent of the US Navy.
CVN-77 George HW Bush - Combat flight officer/pilot during World War II who was shot down and who later was a war President through Desert Storm.
CVN-78 Gerald R. Ford - US Navy combat officer in World War II and later President of the United States.
CVN-79 John F. Kennedy - US Navy combat officer in World War II and later President of the United States
All of these are acceptable to me (some more than others), and were given those names in accordance to their accomplishments as leaders (both military and in public service) who influenced key issues (either in combat or otherwise) that had significant impact on naval matters or those of the overall nation.
It is when names are given out as political awards and for purley political purposes to individuals who had no such impact or involvement, or who exhibited their own disdain for America's military personnel, that, IMHO, the line is crossed.
Caesar Chavez and John Murtha are a couple of examples. There are several others.