Besides class, the other question regarding this strapping son of Big Brown is how far he will want to go. So far, Big Brown has been more a sire of milers than anything else, although his son Ground Transport is a stakes winner at 10 furlongs. The 3x3 cross to Danzig in Dortmund's pedigree also suggests "miler" more than "stayer." In current American racing, though, a miler with a high cruising speed can be a dangerous customer in longer races if given a favorable trip, so Dortmund certainly can't be counted out of the Triple Crown picture this early on that score.
The dam line is also rather ambiguous. Dortmund's dam Our Josephina was a stakes-winning sprinter but in fairness was not really given a chance to be anything else. Her sire, Tale of the Cat, scored his biggest win at 7 furlongs and is similarly bred to to Johannesburg, a champion juvenile who failed to train on. Her dam Ropa Usada (by Danzig) did not race but is a half sister to 1985 Champagne Stakes (USA-I) Mogambo (by Mr. Prospector), another horse who was essentially a miler. The nearest confirmed source of stamina is Dortmund's third dam, 1977 American champion juvenile filly Lakeville Miss, who trained on to win the 1978 Coaching Club American Oaks (USA-I). That's not all that reassuring, but then, Big Brown himself is really more a miler-bred type, and look what he accomplished. Like father, like son? Could be.