One win on the road will make their chance alive in the series as most likely they can win the game 6 at home, people really hoping for him to come back.
Now Game 5 will be on the Raptors home and a chance for them to get their first championship. The odds are favoring to them. Klay played well on Game 4 but Curry didn't contribute that much to the game. He is well defended so the Raptors held him with under 20 pts IIRC. If Durant will not play on Game 5, its a game over for them but if he will play the chances of them winning on the road will increase a bit.