If Japan had not attacked Pearl Harbor, the outcome of World War II might have turned out completely different. Here is why:
1.) The militarists that control Japan during the war were divided into two groups depending which military doctrine they supported: the Hokushin-ron or the Nanshin-ron.
Hokushin-ron - Northern Strike. These Japanese warlords focused on expanding their empire on the Asian mainland. This meant conquering the rest of China, and going to war against the Soviet Union. Northern Strike enthusiasts were mainly brushed aside after the Battles of Khalkhyn Gol (1939), a border skirmish in which the Soviets and their Mongol allies dealt the Japanese military a swift and decisive defeat.
Nanshin-ron - Southern Expansion. Supporters of this doctrine wished to occupy the resource rich areas of Southeast Asia. This put them in complete conflict with the European powers that controlled the region: France (Indochina), Great Britain (Honk Kong, India, Burma, Malaysia, and Singapore), and the Netherlands (Indonesia). The Southern doctrine also targeted America, which controlled the Philippines, several strategic Pacific Islands, and the largest naval force in the region.This strategy was more appealing due to the resources in the area, Japan basically has no natural resources, and the fact that the European Powers were preoccupied with Hitler.
The only way Japan would not have attacked Pearl Harbor is if they went North rather than South. I would imagine that being invaded from both the East and West would have been too much for the Soviet Union to handle. The USSR would most likely have surrendered to the Axis powers. Even if this was the case, Japan would have most likely turned back to the Southern Doctrine once the USSR was defeated due to the resources it could have supplied for the empire.
Could Pearl Harbor have been avoided? I personally do not think so. if the Japanese did not attack on December 7, 1941, they would have attacked eventually in the future.