The next chapter of CBS Corp.’s ongoing feud with Shari Redstone is set to turn on the validity of a board of directors’ vote late Thursday to strip its controlling stockholder of her voting power and whether Redstone’s National Amusements Inc. has the authority to block the move.

While a leading observer expects Redstone to make the next move, it was uncertain at the end of a dramatic week whether she or the CBS board would act first in their battle for control of the company, and over a potential merger of CBS into Viacom Inc.