On the Family Guy panel at this year's Comic Con showrunner Steve Callaghan confirmed that a Griffin family member would perish and be replaced by a new character in the upcoming series. He denies that it's Peter's mother Thelma, who dies in an upcoming episode (possibly due to the real life death of Phyllis Diller in 2012, who voiced the role after taking over for Florence Stanley when she passed away in 2003) but verified that it would be one of the six main characters, though he would not say who exactly.
