It feels like a weird comment for the campaign to make. "We have momentum now, so we don't want another debate." generally translates to "We think that debates will probably do more harm than good to our candidate."
The "conditions" feel like they're simply a ploy to avoid the one being discussed right now. The DNC isn't going to agree to them, and O'Malley probably isn't even going to be running by then. And they know this.
They're probably hoping O'Malley will stay in longer and eventually go negative so they won't have to.