Nonagenarian media mogul Sumner Redstone has given up his executive chairman position at CBS Corp., the company said late Wednesday afternoon. CBS Corp. president and CEO Leslie Moonves has been elected the next chairman of the CBS board of directors, and Redstone is now chairman emeritus.

Redstone still technically holds 80 percent of the controlling shares of National Amusements Inc., which in turn holds 80 percent of the shares of media companies Viacom, of which Philippe Dauman is CEO, and CBS Corp.

Redstone’s daughter Shari E. Redstone holds the other 20 percent of National Amusements and sits on the board of directors for CBS Corp. and Viacom.

Dauman, though, might not want to hope too hard to fill his company’s chairman position. He is currently one of the seven trustees who will manage the trust that Redstone’s shares will go to in the event of his death. Shari Redstone released a statement indicating that running the Viacom board and being a National Amusements trustee would be too tangled a web: 

“As has been accurately reported, my father’s Trust states his intention that I succeed him as (non-executive) Chair at CBS and Viacom, and also names me as a Trustee after his death. However, it is my firm belief that whoever may succeed my father as Chair at each company should be someone who is not a Trustee of my father’s trust or otherwise intertwined in Redstone family matters, but rather a leader with an independent voice.”

Viacom’s response: “The Viacom board of directors is scheduled to meet tomorrow.­”

Shari Redstone nominated Moonves to fill the position vacated by her father, the perhaps slightly early fulfillment of a reported pact between the two that was supposed to occur after the Redstone patriarch’s death.

“I want to thank Sumner for his guidance and strong support over all these years,­” Moonves said in a statement. “It has meant the world to me. I am particularly grateful that Shari Redstone has agreed to continue in her role as Vice Chair of the Company.­”

The move is hardly unexpected, though the timing is fortuitous. Redstone, 92, is at the center of a couple of legal battles over his healthcare and mental competence, though a judge recently ruled that he would not have to be deposed.

Moonves addressed the issue of the lawsuits at an investor conference in New York in December: “It hasn’t been a distraction. We are very secure. We’ve been running the company very well, and the future looks very bright, and not much is going to change.”

CBS Corp. reports its fourth-quarter earnings on Feb. 11, but in reaction to the news, after-hours trading sent CBS stock up an additional $2 from its closing price of $48.28, which was itself up $1.65, or 3.54 percent, for the day.