I also mentioned in my email to you that no additional allegations had been made by the staff. Please note that since that email, an amended notice of allegations containing one additional violation related to the first allegation was issued to the involved parties.
On Monday, the enforcement staff conducted another call with institutional officials and determined that it is possible to move forward with the August 12 hearing while acknowledging the additional review is necessary. At this point in the inquiry, the available evidence does not warrant additional allegations; however, the investigation remains open. As a result, the staff and institution agreed not to postpone the currently scheduled hearing date of August 12 while we finalize the investigation of the remaining open issues. The institution understands and agrees that additional allegations may result from the ongoing inquiry and that the violations set forth in the current notice of allegations may form the partial basis for a failure to monitor of lack of institutional control when viewed in light of any additional violations. The institution also understands that if new violations are discovered, a second hearing may be necessary.
[...] the continuing investigation could potentially lead to additional allegations involving Mr. Tressel.
Popular opinion on twitter seems to be that the additional allegation explicitely mentioned in the letter is the addition of Dorian Bell to the list of players wrongdoing. However, the letter makes it clear that this additional violation is not necessarily exhaustive of the potential additional allegations.
But you can't have one without the other. Gene Smith's spin:
We are aware of a letter that the NCAA enforcement staff sent to the Committee on Infractions nearly a month ago detailing the status of this case. The NCAA staff concluded that the evidence at this time does not warrant additional allegations and that our joint review of any remaining items did not necessitate a delay to today’s hearing. We now look forward to working together so that we can conclude this follow-up work as quickly as possible.