1. families had fewer kids after the 2008 recession.
2. Alternative forms of education.
The latter will be good news, if it does displaced old colleges. The former, which is waaay earlier in the article and therefore probably the more important cause (in the opinion of this article) could be swung at any moment by a change in immigration, welfare, or regulatory policies on state (for the latter two) or Federal levels.
I don't see much reason to take this prediction seriously. Are private investments or bonds of some kind in these institutions tanking?
Cost of tution/student/mo = 6hr * 5day * 4 weeks * $50/hr / 20 students = $300
Cost of facilities/student/mo = $600
Cost of room and board/student/mo = $600
So at minimum student will need to bear $18000/yr cost. If college is only receiving fraction of this then it will bankrupt.