An October Surprise is supposed to be delivered right before the election so as to be fresh in the voter's mind and to not allow for rebuttal or counter-spin. In 2000, the Gore Campaign delivered a November surprise on George Bush, revealing a long-obscured drunken driving offense the weekend before the election. It probably damaged Bush's campaign and might have cost him the popular vote.
If Assange has airtight documents that will destroy Hillary, he should have released them a long time ago. Crooked Comey has set the bar of prosecution to a height never before imagined. He has before him, enough evidence to convict Hillary of data security violations, influence peddling and even, quite possibly, espionage. Still, he refuses to recommend prosecution.
Had Assange delivered a bombshell, Congress could have acted to demand a special prosecutor. Now, they are in recess so they can hit the campaign trail. Nothing, as in absolute zero, would ever force Loretta Lynch to do her job. She has already earned herself induction into the Political Corruption Hall of Fame. The media will gloss over the accusations, no matter how horrendous they might be, and Hillary will run out the clock. Checkmate.
Assange might have been using the threats as a bargaining chip to escape prosecution on espionage and trumped up sexual assault charges. He might not have that ace in the hole after all. If he does show his cards and they are worth viewing, the revelation will be met by a canned response of "At this point, what difference does it make?" Electorally, probably none.