It is my understanding that there is a rev limiter built into the computer and it will not let you rev past the "red line" point. Ford is known for having conservative tunes and I wouldn't be surprised if the FEH has an arbitrarily low RPM limit in it's tune. I make it a point to stay below/around 6,000RPM on the rare occasion that I need full power and I didn't go above 4,500 for the first 3,000 miles.

I did some looking and I see where the Duratec 2.3 I4 in the 2007 Mercury Milan has a 6800RPM red line (would the Atkins cycle affect max RPM?) and several other Duratec motors are well into the 6000s before they reach full power. In the day and age of drive-by-wire and thus fully computer controlled fuel and spark, there's no reason that an engine should go past the computer controlled limit (unless someone "tweaked" the computer).

I don't think you'll see a rush to remove the rev limit on an FEH as RPMs beyond 6000 are probably returning less power than other lower/less stressing RPM zones. If anything you'll see a tweak in the electric side before you'll see one on the ICE side.