Sorry for taking so long to get back to you. I don't think it would be considered a material event. As important as a Markman ruling is in a patent case, a "material event" is a specific, legally defined thing. It is a hard, cold fact that will without question affect a company in a positive or negative way. Think of an oil company that discovers a new, huge deposit of oil. A Markman ruling, and probably most things that happen in court, is just not that kind of sure thing. Judges and juries are pretty unpredictable sometimes.
Best of luck.