In addition to the grief around Paul Walker's unexpected death, there is a problem due to the fact that he was in the middle of filming a movie. Previously it was announced that Fast and Furious 7 had been put on an indefinite hold, but there is now some talk that the film may be scrapped and started from scratch with a new script that excludes Walker's character.
Fast and Furious 7 was already halfway finished filming, but most of the key scenes involving Paul Walker were not completed yet. The big concern by Universal and director James Wan is how to move forward without tarnishing Paul Walker's memory and disrespecting the fans. In addition to the production indefinitely stopping, another option being explored is to restart and basically cut out Walker's character altogether. Personally, I find that the most disrespectful option.
The other option is to do rewrites and try and work around the scenes that were not filmed yet. There is a big possibility of body doubles, like what they did when Brandon Lee died during filming of The Crow, so fans can kind of feel like they are saying goodbye to Walker while seeing him on-screen one more time. One minor detail with this thought is the potential for CGI to be introduced and have Walker's face digitally placed onto a double.
The bottom line is there is no getting around that Walker starred in a franchise about street racing and died in a fiery car crash. It is very sad, don't get me wrong, but it is just a fact. I think the best thing they could do would be to just move forward. It isn't disrespectful to, for lack of a better way, kill off Walker's character. If they still want to make the July 11th release date they are going to have to make some decisions fast.