An option that no one has mentioned is to make a converter from the traxxas plug on the ESC to deans plugs. They're no loss connectors so one extra connection shouldn't be an issue.

But, if it were my choice, I'd change the Traxxas stuff to Deans. The Deans are, after all, a proven system and changing one or two lpugs makes more sense (and is cheaper) than changing all the batteries and the charger.