I think the F-150 is one Ford you won't need to worry about. Two things that Detroit really knows well are pickups and loopholes. They aren't going anywhere, and it is unlikely that capability will decrease.
In fact, the F-150 came about because of this kind of thing. Due to new emissions requirements in the 1970s, Ford had to use smaller engines with cats on the F-100. The F-150 was introduced, with a higher GVWR than the F-100, which made it exempt from new regulations.
Many of the current 1/2 tons are excessive in every way, and they still have managed to get fuel economy up into the low 20s. You may see fewer crew cab, big V8, loaded pickups in the future, but the pickup itself won't go anywhere. Ford and the others are certainly capable of building efficient trucks with high payload and towing capacities, but until now it has been more profitable to build crew cabs with features comparable to luxury cars and big V8s.
Here is something to think about. You can get a basic I4 Ranger with a payload capacity over 1500 lbs. Guess what the payload capacity is for the typical loaded crew cab luxury 1/2 ton with a big V8? Around 1500 lbs., and often times less than that. Many are in the 1000-1300 lb. range. It isn't fuel economy or the government that has been holding back capability until now, it is all the khrap that people insist on having to keep up with their neighbors. Maybe the new regulations won't be such a bad thing...it will force truck makers to get back to the basics.