More Big Love updates today. Beginning with today’s least pleasant news, according to TV Guide Online, actress Amanda Seyfried will be leaving the Big Love cast soon in order to better focus on a career in film. Seyfried, who portrays Bill and Barb’s eldest daughter Sarah on the show, has been onboard since Season 1. According to the source, her departure at the end of Season 4 has been confirmed. We’re, of course, very sad to see her go. More information is available at TVGuideMagazine.com.

In a later report, TV Guide brings up the possibility of former child star Macaulay Culkin, best known for the 90′s Home Alone films, joining the cast next season (though please bear in mind a 5th season remains to be confirmed by the HBO). According to the source, Culkin has been spotted visiting the set of the show and he also shares the same agent with actress Sissy Spacek, who currently has a regular guest role on Big Love as lobbyist Marilyn Densham:

Mac, who (believe it or not) turns the big 3-0 this summer, was recently spotted on the Big Love set, where he visited with pal Chloë Sevigny (Nicki) and cocreator Will Scheffer. “We’re interested in him,” Scheffer says. “He watches the show and we can see him fitting into either the compound or the Mormon world.”

Turns out Macaulay shares the same agent with Sissy Spacek, who’s on the series this season as a powerful lobbyist and may return for Season 5. So who would Mac play? With plans to “expand our show’s youth franchise” in 2011 (pending a renewal from HBO), Scheffer says Macaulay would be “an interesting person to add to that mix.” Star Bill Paxton’s suggestion: “He’d make a great young evangelist.” Amen!

Finally, as usual, here is the trailer for next Sunday’s Big Love episode, 4.04 “The Mighty and Strong”, courtesy of HBO: