Hmm, should have stopped on runway for sure BUT this incident will probably highlight the fact that contaminated performance is at best a shot in the dark, an estimate of what might happen. Very little of this data is supported by flight testing in the actual conditions and it's only when you come to do a high speed reject on a contaminated runway that the limitations of the data, the runway reports and the tables become apparent. I am willing to bet that, despite the inbuilt safety margins, a large percentage of limiting, contaminated runway departures would result in an overrun in the event of a high speed RTO.