4-conference, 16-teams each playoff arrangement is gaining steam. If that happens, then it would be a faster decline. If not, it would take more time...similar to the 15-202 year time frame you mentioned.
The lack of attendance (and overall interest) in the non-playoff bowl games, including the NY6 games probably pushes that idea along, IMO. They're going to do something to salvage interest in the "pinnacle" of the season... but no one cares outside the 4-team playoff.