It was pre-taped a few weeks ago in line with Jeopardy's usual schedule. There were a number of untelevised practice sessions beforehand against other Jeopardy contestants and wannabes. IBM did their tweaking then and promised that the actual competition rounds would be televised regardless of results.

Also if IBM were to cancel an episode that showed bad results, it'll eventually leaked out, especially for project of this caliber. It would be an instant negative publicity, since EVERY tech site would pick it up.

You'll have the scorn of all the geeks on the internet, which could be interesting lol