Will Mike Duke retire in 2013?

Wal-Mart Stores, Inc., president and CEO Mike Duke claims to love working for a company where success and size have resulted in high expectations, but that love affair may be ending in 2013.

Speculation regarding Duke’s tenure as CEO is nothing new. It began in the fall of 2008 as soon as it was announced he would succeed then president and CEO Lee Scott. Duke was 58 at the time and only one year younger than Scott, so he was never viewed as the same type of long term leadership solution that Scott was. Scott was 51 when he took over the top job in early 2000 from former president and CEO David Glass who was 64 at the time of his retirement.

Duke is now 62 and halfway between the age at which Scott and Glass gave up the post.

As Duke prepares to enter his fifth year as CEO, following four grueling years as vice chairman responsible for Walmart International, chatter has begun to heat up regarding the timing of his eventual retirement and potential successors. Adding fuel to the fire is the company’s ongoing investigation into possible violations of the U.S. Foreign Corrupt Practices Act. Initially focused on Mexico, the extensive investigation has since expanded to Walmart operations in other regions of the world.

This investigation has been underway for more than a year and cost the company more than $100 million. At some point it has to end and when it does, if there is blame to be assigned or assumed, it could well be Duke who ends up taking the bullet for the company.

Even if that proves not to be the case, Duke may simply decide that 2013 is the right time for him to step down following a lengthy retail career. If so, the list of potential internal successors basically consists of Walmart U.S. president and CEO Bill Simon, 52, and Walmart International president and CEO Doug McMillon, 45. An argument could be made that both men possess the leadership abilities to assume the top job which is a high quality problem for Walmart to have.

Duke’s eventual retirement and new responsibilities for Simon and McMillon will trigger a series of additional personnel moves that could see people like Walmart EVP and chief administrative officer Rollin Ford, 49, assume new responsibilities and open the door for Walmart to elevate additional women to high profile senior leadership positions.

Regardless of when Duke retires and who succeeds him, the job of running Walmart is unlike any other in the world and requires a special skill set. Walmart is poised to surpass $500 billion in annual sales within the next few years, ensuring the company will face enormous operational challenges even as it pursues new growth opportunities while simultaneously defending itself from criticism that never seems to fade regardless of the company’s actions.

That said, Walmart is for the most part in a good place with momentum on its side. The FCPA investigation is a huge dark cloud, but Duke contends it will make the company stronger.

"Because of our success as a company, we do face higher expectations from our customers and our associates in all areas," Duke said in a memo to employees earlier this week. "I love that the world looks to us as a leader.　Walmart has an influencing role, and we must lead by example and help raise ethical standards overall.　As I have said all along, we will use these events to raise the bar and make Walmart an even better company.　We have ensured that the ongoing investigation has the time and resources it needs to get to the bottom of what happened."

Walmart has offered no indication on when it will get to the bottom of what happened, but if doing so results in a leadership transition Walmart may want to dust of the quote it used in the press release back when Duke was named CEO.

"This management change occurs at a time of strength and momentum for Wal-Mart," said Rob Walton, chairman of the Wal-Mart board of directors. "Our overall management team has never been stronger. We are confident that the strategy we have in place is the right one for future success and Mike has been actively involved in developing and executing this strategy. We are also pleased that our succession and management development process continues to develop leaders internally."

It’s is not hard to imagine Walton saying the same thing about a transition involving Simon or McMillon, whether such a change occurs in 2013 or beyond.