Who cares?
Not to be over cynical about a show that made cynicism its motto, but I don't think, for a moment, this stunt is going to stick. This is as permanent as when DC tried to kill Batman, and Marvel did the same with Captain America. Remember that episode that ended with Stewie "finally" killing Lois? How permanent was that? In a couple episodes, it will all be revealed to be a dream, Ryan will be resurrected with pseudoscience (or even magic, since the show is not above that), his ghost will became a regular character or the new dog will be replaced with someone that is pretty much just exactly like Ryan.
I give it 3 episodes. If in the next 3 episodes Ryan does not reappear within the main cast in one way or another I will consider myself corrected. in any case, I won't particularly care about that since I don't watch the show regularly to begin with...