While the prognosis for Dimon's recovery is good, JPMorgan's board of directors should consider a succession plan, Sonnenfeld said on "Squawk Box."
After all, Dimon is such a strong leader that if JPMorgan does not consider who will follow him, the banking giant could lose its way.
"It is not exploitative, I think, to take a look and make sure this board has deep bench strength and they do," he said.
Possible successors include Gordon Smith, CEO of consumer banking, Mary Erdoes, CEO of asset management and Daniel Pinto, CEO of corporate and investment banking.
To Sonnenfeld, Dimon has done a good job of raising the profile of these executives. But in any case, Dimon will be a "tough act to follow."
"He is absolutely iconic. He is probably the most feared and revered man in finance today. ... He has proven himself many times over," Sonnenfeld said. "He's a comeback superstar in his personal career and also in the, what, 48 percent return in stock price in this company and despite the crazy pounding of some of those penalties they had to withstand. Still, they turned out record profits."
—By CNBC's Drew Sandholm.