"Downton Abbey" back on Jan. 4 for season 5

"Downton Abbey" will be back for its fifth season on Jan. 4, but the return date for another hit PBS series, "Sherlock," is up in the air, PBS chief executive Paula Kerger said Tuesday.

"We will have to wait to know when it's finished and available," Kerger said of the mystery starring Benedict Cumberbatch. "Whenever it comes, we'll put it in a wonderful place."

PBS is making its shows available for flexible viewing, using both digital platforms and creative scheduling on public TV stations, she said. All episodes of Ken Burns' "The Roosevelts," for instance, will be available for streaming the day after the first episode airs on Sept. 14.

Don't expect the same treatment for stately manor soap opera "Downton Abbey."

"Downton Abbey' will have some surprises in it. I think you know what's going to happen to the Roosevelts," Kerger said.

Looking ahead, executive producer Gareth Neame recently gave some hints about how he'd like the series to end, telling TV Line, "In whatever the storylines end up being, I think people will want some sort of resolution. I'd like there to be some sort of message where you get to the end of it all and you say, 'Oh, I see. So Anna Bates is my grandma.' I don't know how we'll do this, but I've always loved the ending of 'Schindler's List' when they cut to the piece in color, and they're all putting the stone on the monument. I loved the way that connected the Second World War, which none of us lived through, to people who were still alive today. I'd love to somehow deliver that message."

Other PBS announcements from Kerger:

- "Walt Disney," a four-hour, two-night film about the life and legacy of the entertainment groundbreaker, will air in fall 2015 as part of the "American Experience" series.

- Kristin Chenoweth will serve as host of PBS' fall arts festival featuring theater and music on Friday nights starting Sept. 29. Productions include "Sweeney Todd: The Demon Barber of Fleet Street," "The Gershwins' Porgy and Bess," Tony Bennett and Lady Gaga performing on "Great Performances," and the special "Kristin Chenoweth: Coming Home."

- Drama series "Call the Midwife" will return for a fourth season on March 29.

- "The Brain with Dr. David Eagleman," described as a "visually spectacular journey" into the human brain, will air as part of the "Think Wednesday" lineup of science and nature programming in 2015.