Russell as Ego appears set to portray one of several new characters known as the Elders of the Universe, a group of ancient beings who are the last of each of their races. Some of these roles have already been cast, but not fleshed out or fully realized, whether in Guardians or in other movies in the Marvel Cinematic Universe. A new report, however, indicates that they will play a significant role in Guardians of the Galaxy 2 and other movies leading up to the climactic battles of Avengers: Infinity War.
Schmoes Know claims that The Elders will be an integral part of Guardians of the Galaxy 2. The report describes The Elders as "the impetus for Star-Lord to seek out Ego the Living Planet," indicating that they will be a significant in driving the plot. There are reportedly at least four Elders in Guardians 2, but only two that are definitively known: The Collector, played by Benicio del Toro in the first Guardians movie, and Ayesha, played by Elizabeth Debicki (The Night Manager). Director James Gunn has previously said that The Collector would not appear in Vol. 2., but Schmoes Know's report disputes this.
Ayesha is not an Elder in the original comics but Schmoes Know speculates that her character will "morph a bit" and become one in the MCU. The other two known Elders will be played by Sylvester Stallone and Sharon Stone, but have not been named yet. Jeff Goldblum (Independence Day: Resurgence) will portray the Elder known as The Grandmaster in 2017's Thor: Ragnarok but any connections to Guardians 2, if any at all, remain unknown.
The official details regarding Stallone and Stone's Elder characters remain nonexistent, and there's now way of telling how accurate these rumors are. There are over a dozen original characters from the comics to choose from, which makes their roles anyone's guess at this point. But the Elder character that appears to fit Stallone's image and persona is The Obliterator, a powerful hunter-type adversary for the Silver Surfer who carries his own body-mounted weaponry. Stone, meanwhile, could be in line to portray some version of The Caregiver, a female Elder who originated in the Quasar comics in 1992.
UPDATE: James Gunn, for his part, has now publicly dismissed these particular Guardians of the Galaxy Vol. 2 rumors.
Doctor Strange opens November 4, 2016; Guardians of the Galaxy Vol. 2 – May 5, 2017; Spider-Man: Homecoming– July 7, 2017; Thor: Ragnarok – November 3, 2017; Black Panther – February 16, 2018; Avengers: Infinity War – May 4, 2018; Ant-Man and the Wasp – July 6, 2018; Captain Marvel– March 8, 2019; Avengers 4 – May 3, 2019; and as-yet untitled Marvel movies on July 12, 2019, and on May 1, July 10, and November 6 in 2020.
Source: Schmoes Know
Update Source: James Gunn