According to THR, Universal has enlisted writer Chris Morgan to try and salvage footage already shot, in order to try and give Paul Walker's character a proper "retirement". So it sounds as if Universal has made the wise decision and chosen not to kill Brian O'Conner off from the franchise, choosing to let him go quietly into a life of parenthood. If Morgan can do it, and really the chances of that are pretty slim, then production could start back up in January.
Assuming Morgan can't do it, then Universal will have to go with their recently-revealed plan of scrapping the entire thing and starting over. The film is heavily insured so it's not as if money is a concern, although the $150M insurance claim they would have to file would be the biggest in Hollywood history. In other words they've already poured in a great deal of cash on this film so they may as well make sure it gets done in a way that satisfies and respects everyone involved. There are no plans to end the franchise, either, as they intend to move forward on an eighth movie and probably a ninth.
Universal is already preparing for the film to not hit the target release date next summer by moving Dawn of the Planet of the Apes up a week into its July 11th 2014 slot.
