IMHO, WWOHP has stolen business from WDW. However, given WDW's attendance over the last 10 years, I politely suggest that a poor economy has taken a bigger bite out of WDW attendance than WWOHP. For example, WDW was much more severely impacted by the post 9/11 economy than it was by the opening of WWOHP. Don’t get me wrong, I think WWOHP is the best "land" in all Orlando. It certainly has turned around UO. However, given that this thread is titled, NYT: "Universal....Takes Aim at Disney", it does not appear to me that UO has seriously damaged WDW's long-term revenue stream. Fundamentally, I don't believe UO ever will until it figures out a way to appeal more strongly to the small child crowd.
Please understand that I really enjoy UO and think it has 3 of the best 5 attractions in Orlando (FJ, Spiderman, Mummy). I just don't think it presents a significant risk to WDW's dominance at this time.