There’s little doubt the JPMorgan Chase bench is deep, but at the moment, there is no obvious Dimon lieutenant with Mr. Dimon’s stature, and it’s reasonable to think he prefers it that way.

At Goldman Sachs, the leadership dynamic is slightly different. Like Mr. Dimon, Lloyd C. Blankfein, 61, has been chairman and chief executive a long time, since June 2006, when his predecessor, Henry M. Paulson Jr., left the company to become George W. Bush’s Treasury secretary. Mr. Blankfein steered Goldman through the worst of the financial crisis in impressive fashion — including years of record profits, since diminished — while also overcoming a tsunami of awful publicity.

In September 2015, Mr. Blankfein announced that he had a “highly curable” form of lymphoma and, according to Gary D. Cohn, the Goldman president and chief operating officer who has been thrust into the role of Prince Charles for nearly a decade, Mr. Blankfein is “in the office every day” and “engaged.” The days he is not in the office, “he’s on the phone all day long,” Mr. Cohn said.

Mr. Cohn has said his relationship with Mr. Blankfein has never been better, even though many have wondered how long he will wait for his chance to run Goldman. A few weeks ago, The New York Post reported that Mr. Blankfein, who has declined recent requests for interviews, made a rare appearance at the annual Goldman alumni event, where he seemed to be his “old jovial self” and reportedly said he intended to be running Goldman for “a long time to come.”

At Morgan Stanley, 2016 ushered in an old-fashioned power play. James P. Gorman, 57, the bank’s chief executive for the last six years, conveyed to employees his intention to stay put for at least another five. He also announced that he was appointing Colm Kelleher the company’s sole president. (Mr. Kelleher, a year older than Mr. Gorman, is unlikely to succeed him if Mr. Gorman sticks around for the full five years.)

Mr. Gorman’s decision led to the somewhat surprising departure of Gregory J. Fleming, 52, who ran Morgan Stanley’s wealth and asset management businesses. Many observers figured that Mr. Fleming would one day run Morgan Stanley, given its shift toward the more predictable earnings stream generated by managing customers’ wealth. But as The New York Times reported, the company seems to be struggling to find its strategic direction. In any event, Mr. Gorman is not going anywhere soon, and the succession picture at Morgan Stanley has become a cloudy one for the post-Gorman era.