Fast & Furious 7 was put on indefinite hold, according to Universal. The news announcing Paul Walker's death has shocked and saddened his many fans, and the actors he worked with are grieving the loss of someone who was also a good friend.
The car crash that ended Paul Walker's life could be turned into a plot device that could ultimately strengthen the film, even if it may end up being the last film in the series. Critics around the world have probably been hoping the series would end anyway, but The Fast and the Furious has actually gotten better over the years.
In my honest opinion, it was always Vin Diesel who carried the series. True, he's not much better at acting than Paul Walker was, but if it wasn't for him, would we have even been interested in the first film?
2 Fast 2 Furious didn't have him in it, and it was the worst film in the series.
Tokyo Drift had Vin Diesel for a few seconds at the end, but no Paul Walker, and it was a better film than the one previous. Fast & Furious 7 could actually be better than we expected now.
This is not disrespecting Paul Walker as a person, to be clear.
The plot for the next film could start with Paul Walker's body double, with maybe a few seconds of face mapping to make it look like him. He'll be out just having a leisurely cruise when something goes wrong with the car, making it crash and killing him instantly. We will see Brian O'Connor die on screen, and when Hobbs (Dwayne Johnson) investigates, he discovers that Ian Shaw (Jason Statham) had set the whole thing up out of revenge for his brother. This way, Brian O'Connor is no longer needed, and the motivation is much stronger to go after the villain. Fast & Furious 7 will have a deeper emotional impact, making it a more exciting film.
If there is no compromise and the character must be in the film for it to work, there is another option. Recasting Brian O'Connor might not be a popular idea, but it could work. My suggestion is Luke Goss from Death Race 2 and 3, Hellboy II, and Blade II. He has already shown he can act in an action film, and he carries some of the same attitude that Paul Walker had.
With these suggestions, the tragedy of Paul Walker's death doesn't need to be the end for Fast & Furious 7.