I'm a pescatarian so my experience is probably less helpful but after having been served an Asian vegetarian once when my flight was upgraded about 28 hrs before the flight, I make a point of getting the AVML request removed from all upgraded reservations. It was basically Y food on nicer plates. Depending on your ability to eat around things, you should be fine. Frankly, I should think that between the bread, cheese, salad, and desert, you should have more than enough food. I wouldn't, however, count on their being a vegetarian entree. At least on transpacs to/from Japan, there's invariably a meat main, a fish main, and a Japanese meal.