LOS ANGELES — Disney’s third-oldest theme park, Epcot, is overdue for a serious sprucing up. Is Disney finally ready to write a check?

Bob Chapek, the chairman of Walt Disney Parks and Resorts, hinted last November that major changes were coming to Epcot, which sprawls across 300 acres as part of the four-park Disney World complex near Orlando, Fla. At an event for Disney fans, Mr. Chapek said the 35-year-old Epcot, best known for the giant golf ball-looking sphere at its entrance, would one day become “more Disney, timeless, relevant, family-friendly.”

Mr. Chapek is expected to announce specific plans on Saturday at D23 Expo, a biennial convention for Disney fans that attracts an estimated 100,000 people to the Disneyland Resort in Anaheim, Calif., over three days. A major new roller coaster — perhaps themed to “Guardians of the Galaxy,” the hit Marvel movie series — is planned for Epcot’s front section. Also expected are a ride based on the Pixar film “Ratatouille” and at least one new country pavilion (most likely Brazil) for the park’s World Showcase area.

Analysts also expect Mr. Chapek to unveil more “Star Wars”-related offerings at Disney World. In recent months Disney has surveyed visitors about interest in a luxury hotel that makes guests feel as if they are sleeping on an actual “Star Wars” starship.

And might a Mickey Mouse-themed attraction be replacing Disney World’s dusty Great Movie Ride?

Disney is counting on its theme park division to help offset slowing growth at ESPN. Last year, Disney parks generated $17 billion in revenue, a 5 percent increase compared with a year earlier, and $3.3 billion in operating income, a 9 percent increase.

In particular, Disney has been pouring money into Disney World. Robert A. Iger, Disney’s chief executive, wants to use technology to make its parks more immersive and relevant to a new generation of children. The expansions are also designed to make each of Disney World’s four major parks — the Magic Kingdom, Epcot, Hollywood Studios and Animal Kingdom — an equally powerful draw for tourists. That might help better distribute crowds across the resort.

Most people, for instance, make a beeline for the 110-acre Magic Kingdom, where attendance totaled roughly 20.4 million last year, and then add on half-days at parks like Epcot, which hosted about 11.7 million visitors last year despite being more than twice the size of the Magic Kingdom.

Disney World, which is gearing up for its 50th anniversary in 2021, also faces stronger competition from nearby Universal Orlando, which is undergoing a building boom of its own.

In 2012, Disney opened a $500 million expansion of Fantasyland at the Magic Kingdom. Animal Kingdom recently unveiled a $500 million addition, with an “Avatar” theme, that has been mobbed by visitors. (Lines for some of the new “Avatar” rides initially stretched to three hours.) Hollywood Studios is in the midst of what Bank of America Merrill Lynch has estimated is a $1 billion project to add myriad “Toy Story” and “Star Wars” rides.

Upgrades and expansions to Disney-owned hotels (Polynesian Village, Coronado Springs, Caribbean Beach) and Disney Springs, a shopping and dining district, are costing hundreds of millions more.

That leaves Epcot.

Epcot has not been entirely ignored. Last year, Disney gave an older boat ride housed in the park’s Norway pavilion a “Frozen” retrofit. But large areas of Epcot have become painfully outdated. One ride (scheduled to be replaced) is essentially a 45-minute celebration of fossil fuel; slow-moving vehicles move past dioramas explaining the history of oil, natural gas and coal. A boat ride called Living With the Land takes riders past agricultural scenes.

Many Disneyphiles love that certain Epcot attractions (Spaceship Earth, a jerky tour through world history that is housed inside that golf ball) have remained trapped in amber. But the recent popularity of the new “Frozen” ride has sent an unmistakable message to Disney’s corporate offices: Epcot needs more character-themed attractions to compete for the attention of children.

In many ways, Epcot is Disney’s quirkiest park. It was initially conceived by Walt Disney himself as an actual city called the Experimental Prototype Community of Tomorrow. The company eventually scrapped that plan after his death but kept an educational focus, dividing the park into two main areas, Future World and World Showcase, a constellation of pavilions representing the food, architecture and history of nations like Japan, China, Canada and France. The park was called Epcot Center until a mid-1990s rebranding.

Epcot has lately been best known as a type of festival grounds, with offerings aimed at older visitors that include a lavish flower and garden gathering in the spring and a popular food and wine event in the late summer and fall.