I have checked Transfermarkt for further information about Neymar's current condition. It says that his return date is still unknown. Even though people are staying positive about his return soon I'm not that much sure for now. Missing the rest of the group matches will be bad for him of course.
As for the team they can find a solution to this actually. Because Brazil's most effective line is attacking obviously. There are so many talented wingers in the squad already. For example, Antony can fill his place as a player who can play on both wings.