"The Wedding of River Song" gives no date of the Brigadier's death. We don't know when the Doctor called the nursing home. There's no evidence to suggest he died in 2011 so it can still match the continuity of the novel "The King of Terror" (novel). However, there's nothing to suggest that the Brigadier passed away in 2050 either. Keep in mind also that the Brigadier is close friends with a time traveller.
Also "time can be rewritten", so it's possible that the Brigadier's death in 2050 occurred in a timeline that has now been replaced by one in which he died in 2011.