When it ends it be non-linear: the debt system that we've built our economy and currency on is going to eventually throw up all over itself as we reach Keynes' "long run" and, at that point, experience consumers simply won't have the choice to screw themselves with unproductive debt.

EDIT: And, of course, the elephant in the room is the fascist government/corporate cooperation on student debt, which is now larger and more important than credit card debt in the overall economic credit environment. You kill student debt growth, you kill debt growth and, in todays insane economy, that means you kill growth period.