OK, here is what I'm hearing from various wikileaks/anon threads.
The release is NOT off, only a public appearance by Assange on his balcony. The release is still set to go.
Tuesday is the key day. It is an important day for Wikileaks, it is their 10th Anniversary (founded Oct 4, 2006). They want to make it big, explosive, not only for their anniversary but to possibly make enough of an impact to finally get Assange out of the need for protection- basically lay it all on the table and disrupt the system.
Wikileaks has had this for a while, possibly longer than even the DCLeaks docs. This was the dead man's switch insurance policy Assange has mentioned the past few years- if something happens to him, it was to be automatically released.
What is the big dirt? Rock solid proof Hillary Clinton, through an account she set up in Chelsea's name, was paying off government officials, all the way to the White House.
Something supposedly that should also make Trump worry, but he is secondary. They think both major candidates are going to be harmed but this one is really just about Hillary.