It makes sense, as the rear-wheel-drive, truck-based platform that was the jumping-off point for both the original Explorer and the Sport Trac is no more, replaced by a car-based platform that forms the basis of the Ford Taurus and Lincoln MKS.

The Sport Trac was always a niche vehicle, which is probably why Ford never released Sport Trac-only sales figures, instead lumping them in with all Explorer sales. According to sources quoted by Rick Kranz in Automotive News, however, the Sport Trac performed admirably, accounting for anywhere from 20 to 25 percent of Explorer sales over the past decade -- which, a few recent slow years notwithstanding, were impressive.

I'll quote the late, great Hunter S. Thompson here, from "Fear and Loathing in Las Vegas":
A high-powered mutant of some kind never even considered for mass production. Too weird to live, and too rare to die.

Yeah, all except that last part. RIP, Sport Trac.