HAVANA (AP) - Mr Raul Castro announced on Sunday that he will step down as Cuba's president in 2018, following a final five-year term, for the first time putting a date on the end of the Castro era.
He tapped rising star Miguel Diaz-Canel as his top lieutenant and first in the line of succession.
The 81-year-old also said he hopes to establish two-term limits and age caps for political offices, including the presidency - an astonishing prospect for a nation led by Mr Castro or his older brother Fidel since their 1959 revolution.
Mr Diaz-Canel, 52, is now a heartbeat from the presidency and has risen higher than any other Cuban official who did not directly participate in the heady days of the revolution.
"This will be my last term," Mr Castro said, his voice firm.
In his 35-minute speech, he hinted at other changes to the constitution, some so dramatic that they will have to be ratified by the Cuban people in a referendum.
Still, he scotched any idea that the country would soon abandon socialism, saying he had not assumed the presidency in order to destroy Cuba's system.
"I was not chosen to be president to restore capitalism to Cuba," he said. "I was elected to defend, maintain and continue to perfect socialism, not destroy it."
Mr Castro fueled interest in Sunday's legislative gathering after mentioning on Friday his possible retirement and suggesting lightheartedly that he had plans to resign at some point.
It is now clear that he was serious when he promised that Sunday's speech would have fireworks, and would touch on his future in leadership.
Cuba is at a moment of "historic transcendence," Mr Castro told lawmakers in speaking of his decision to name Mr Diaz-Canel to the No. 2 job, replacing the 81-year-old Jose Ramon Machado Ventura, who fought with the Castros in the Sierra Maestra.
Mr Castro praised Machado Ventura and another aging revolutionary for offering to leave their positions so that younger leaders could move up.
Their selflessness is "a concrete demonstration of their genuine revolutionary fiber ... That is the essence of the founding generation of this revolution."
He also said that Mr Diaz-Canel's promotion "represents a definitive step in the configuration of the future leadership of the nation through the gradual and orderly transfer of key roles to new generations."
On the streets of Havana, where people often express a jaded skepticism of all things political, there was genuine excitement.
"This is the start of a new era," said Mr Roberto Delgado, a 68-year-old retiree. "It will undoubtedly be a complicated and difficult process, but something important happened today."