So the Egyptians had a history of attempting to throw off the Persian yoke. A more or less semi-independent Egypt in revolt from Persia (28th-30th dynasties) lasted until 343 when Artaxerxes III was able to successfully invade and restore Persian control over Egypt. But let's say his invasion is repelled and unsuccessful? Alexander crossed the Hellespont merely 9 years later, in 334.
What would be the effects if Egypt is still in revolt? Presumably he would ally with Egypt against the Persians, but would he possibly attempt to take control of Egypt, or let them be as an independent ally while he continues to attack the Persian Empire? I assume he could conduct joint operations with the Egyptians in the Levant? Also, after defeating the Persian Empire, might he turn on Egypt?