By Tuesday, the American Triple Crown will have wrapped up, and the cream of the 3-year-crop will be on their way to late-summer destinations and an eventual convergence with the older-horse set. But across the pond, all eyes will be trained on an English 3-year-old, the best-known sophomore in the world, Frankel, whose next stop in a so-far undefeated career comes Tuesday in the Group 1 St. James’s Palace Stakes at Royal Ascot.