It's important to remember that they found classified material in Clinton's emails before. As Comey noted in his famous press conference and Congressional testimony, the issue of whether or not to indict came down to finding evidence that it was her intent to jeopardize that classified material. Carelessness and negligence were not deemed indictable.
For this new evidence to change the July decision it would have to get through a number of hurdles.
1 Are the emails new or duplicates of previously reviewed emails
2 Are the emails from Clinton herself (not Abedin)
3 Do they contain classified information
4 Do they contain evidence she intended this information to get out of the State Dept.
Then and only then would she be in any legal jeopardy. It is possible Abedin could be in jeopardy, but again there would have to be evidence of intent, not just negligence.
ABC Legal analyst Dan Abrams talked about this on This Week this morning noting
http://www.mediaite.com/tv/dan-abrams-even-longer-long-shot-that-fbi-finds-anything-serious-in-new-emails/