It hasn't always been easy for the Prep since 2000. Between 2004 and 2012 they won a grand total of one league championship--in 2005. They had some very good teams in some of those years but lost very close league championship games to O'Hara ('04), LaSalle ('06, '09, and '12) and to Roman ('07). The other years ('08, '10, and '11) they didn't make it to the championship games, and in Infante's first year ('10) they were 4-7.
Of course, at some point to current run will end. What could be the cause? Obviously the departure of some of the key coaches might make a very big difference. The school could also decide to de-emphasize the sport. (Right now it's clear it has chosen to pay particular attention to the football, rowing, and basketball teams.) Any kind of serious scandal would be a serious blow. And maybe one school or more than one other school could become a real go-to school for kids serious about football. (I think the Prep would like to see other PCL schools, especially the larger ones, get better--but not better than it is!)
Next year they should be really good again, but it would be a surprise if there weren't some kind of drop-off the year after. The current sophomore class has some very good players (e.g., Sacca, West, Roy Turner, and Hardy) but nothing like what the junior class has. I saw the recording of one freshman game and was impressed by how good the team was, so I wouldn't expect a huge drop off after next year.