Usually, it's the Democrats who pull off the October Surprise.
The Access Hollywood tape, released in September 2016, was a surprise for the Dems. Had it been released in late October, Trump would have lost badly. Instead, Comey pulled off the October Surprise, and Hillary lost.
Usually, the October Surprise is something minor, but released just before the election, for maximum impact. Like the Bush DUI news in 2000.
It's unlikely the Dems have anything new on Trump, but they may have a hook for JD Vance. I will let you guess what it is.