no team has won 2 consecutive titles in the BCS era.
winning back to back BCSNCG would also add another perception to a dynasty.
the excerpt below is worth reading. if Bama were to win its 3rd in 4 years, impressive is an understatement in the modern era.
"It is no accident that only one program has built a dynasty in the past 20 years. With no disrespect meant to any team on the list, dynasty came more easily when Notre Dame played a nine-game season in the 1940s, or Alabama played a 10-game season in the 1960s, or even when the Crimson Tide and Miami played an 11-game seasons in the 1970s and 80s. In recent years, national champions regularly play 14 games."