Harold Camping is unlikely to apologize, if he follows the pattern of his predecessors over many millennia.
Fundamentalist Christians are not the only religions or sects to have forecast the end of the world. He may not even admit that he was wrong yet again. He may declare that we now live in a world of illusion.
Helpfully, the Maya had already set a rain date in case the world did not end on October 21, 2011. Now we have to deal with December 21, 2012.
LiveScience October 22, 2011
No Show? Preacher's Doomsday Prediction Echoes Past Failures by Stephanie Pappas. It would probably gall Camping that Pappas may have written this article months ago.
Family Radio has not yet posted its explanation of what did not happen. Its current broadcast is hymns, many about "intelligent design."
From Dallas,
MannaExpress Online Oct. 22, 2011
Harold Camping STOLE My ParentsQuote:
Dear Mom and Dad,
I struggle with how those who believe these things [about May 21st] could, within a weekend, go from bewilderment and disbelief at not being raptured, to absolute certainty that God meant to deceive and shut their eyes to the truth as a part of a big master plan. God sounds like a jerk. An untrustworthy, deceiving jerk.
...
My mouse hovered over the Send button. I closed my eyes and inhaled...and clicked.
Months passed and nothing happened. No response. No acknowledgment. Nothing.
I don’t know what my parents believe about October 21st, Harold Camping’s latest, lamest doomsday date. I don’t know if they believe my family and I are doomed. I don’t know if the warm, loving, dedicated people I once knew will ever pass through the doors of a church again, or whether they will repent.

Edit: Pastor Harold Jeffress of Dallas' First Baptist Church, famous for his views on Mormons and his attachment to Rick Perry and the Dominionists, righteously said
Quote:
“The Bible says that if someone makes a prophecy that doesn’t come true he is to be considered a false prophet and stoned to death,” he told CP [Christian Post]. “Harold Camping has made at least three false prophecies about the day of the Rapture. And so, if he’s not going to be stoned to death, he at least needs to be muzzled.”
...
Jefress [sic] added that Camping is like the boy who kept crying woIf. If Camping and those who want to forecast a date for Christ’s return continue, the pastor asserted, people will not be prepared when the real Rapture occurs.