"If dictator Raul Castro states that he will retire in five years, there will still be no real change for the Cuban people so long as the Castro brothers remain in any form of leadership position, even behind the scenes," she said. "The U.S. should not change its policy of isolation of the Cuban regime."
Fidel Castro is 86 and retired, and has appeared increasingly frail in recent months. He made a surprise appearance at Sunday's gathering, receiving a thunderous ovation from lawmakers.
Some analysts have speculated that the Castros would push a younger member of their family into a top job, but there was no hint of that Sunday.
While few things are ever clear in Cuba's hermetically sealed news environment, rumblings that Diaz-Canel, an electrical engineer by training and ex-minister of higher education, might be in line for a senior post have grown.
In recent weeks, he has frequently been featured on state television news broadcasts in an apparent attempt to raise his profile.
He also traveled to Venezuela in January for the symbolic inauguration of Hugo Chavez, a key Cuban ally who had been re-elected president but was too ill to be sworn in.
The 612 lawmakers sworn in Sunday also named Esteban Lazo as the National Assembly's first new chief in 20 years, replacing Ricardo Alarcon.
Lazo, who turns 69 on Tuesday, is a vice president and member of the Communist Party's ruling political bureau. Parliament meets only twice a year and generally passes legislation unanimously without visible debate.
The legislature also named as vice presidents of the ruling Council Machado Ventura; comptroller general Gladys Bejerano; second Vice President Ramiro Valdes; Havana Communist Party secretary Lazara Mercedes Lopez Acea; and Salvador Valdes Mesa, head of Cuba's labor union.
Anne Marie-Garcia and Paul Haven contributed to this report.
Peter Orsi on Twitter: www.twitter.com/Peter_Orsi