Well, if you want to get to where ALL products are Post-Iacocca-paradigm, I think that year is 1998.
By that point the regular cars were all Cab-Forward, the trucks were all big-rig inspired, the minvan's design cues seemed to heavily follow the Cloud cars, the TJ had replaced YJ, the Cherokee had been refreshed, and we had the Viper. That was also the year that the full-size van got its snout pulled forward for aerodynamics as compared to the less-pointy '94-'97, and crashworthiness and finally got a new interior for at least the driver and front passenger. Certainly the bulk of the van's design dates back to its development during the Johnson Administration, but it somehow managed to adapt to each major era without being outright-replaced.
Then, I think that the next true, nearly complete change is 2007.
The LX has replaced LH. Cloud cars as they were are gone, replaced with JS platform. Neon is gone, Caliber has replaced it. Minivans are on RT platform. '94-'02 Ram has long since been replaced. B-series van is gone, European Sprinter has sort of taken its place. Pacifica is dead-man-walking, Cherokee has been gone for long enough that Liberty is coming up for its redesign, Wrangler has gotten four doors, Dakota has been beat with an ugly stick, Nitro is ramping up, Durango/Aspen are in the mix. Only real holdout that made it much past this is the PT, which survives despite DBAG rather than because of it.
Car companies don't change all models at the same time, that's not practical. But, one can generally look and figure out when the bulk of the cars are on a different paradigm. I'd argue that the Iacocca era was in full swing by 1984 when the only RWD cars left were the M-bodies as holdovers from the seventies and everything else was a K-car, for example.
EDIT: took longer than the five-minutes time difference from Dave's post to type this
