I would not use the word "decline". I believe the IFB movement has evolved. Yes, in the 60s/70s we allowed ourselves to be defined by a handful of mega ministries and conferences. Sadly (but not surprisingly since we were more personality driven than Christ driven) the 80s and 90s were marred by some major and very public scandles, needless inner fighting and some extremism. The result was two-fold: some left the "movement", compromised and became evangelicals. Others just decided to truly become "independent, fundamental baptist". Those of us who chose the latter, still stand strong on what we always considered important, but simply "checked out" of the silly politics. A few national conferences have been replaced by a multitude of smaller regional gatherings, pastors are more focused on reaching their area than impressing some IFB click, many smaller, and regional IFB colleges have replaced the two or three large, colleges. All these things are for the better! Instead of trying to build a mega church, we are getting back to church planting.
I believe the IFB churches (smaller in size, but many more in number and better focused on what is really important) are having a BIGGER impact now (just more quietly) than we were having in the 60s and 70s.
People keep trying to schedule the funeral of the IFB movement -- one problem -- their ain't no corpse! The local bodies are out running buses, soul winning, energizing their young people and reaching the world for Christ!
I don't see that as a "decline"....