This has been an interesting thread to read through. I currently drive a 2002 Tahoe, and plan to keep it until it dies. I like the simple dash and the simple drive train. The last couple of Explorer generations have horrible confusing dashboards. A few years ago when I got the Tahoe, it was a toss-up between that and a 2nd generation Expedition. The only reason the Tahoe won over the Expedition was that the Expeditions were so beaten up around here.
Now for the future, the Tahoe won't last forever. Something will happen and it will cost more that it's worth to keep. I have noticed that the Expedition has less reliance on the touch screen for basic functions than the Explorer, and more physical buttons, which I like. I'd have to actually test drive one to find out, of course. As for Ford engines, I had a 4.6L Grand Marquis with the OHC, so it had long chains too, but no phasers and fewer valves. That engine was still running well and the only significant engine work I ever did on it was to replace the valve stem seals. But the direct injection and boost really concerned me until I found out that Ford started putting in dual injectors. Is there any evidence so far that the intake valves are staying cleaner with this set up? This is the only really issue I have with Ecoboost, and the other members claiming that the previous Expeditions were much more reliable.