IMHO it is rather silly to allude to a 40-year old design in reference to current technology (and disingenuous to grossly oversimplify the comparative problems of '74 vintage 1.6 and 2.0 as being solely a function of displacement and torque). There is simply no meaningful basis for comparing '74 era engines and current designs in a discussion about 'longevity' of the latter.
I predict that the future of internal combustion vehicles will in large part evolve toward using engines in a way that they are almost constantly 'working hard'. That is, the engines will run at peak power and efficiency almost constantly, either delivering motive power directly to the drivetrain or delivering that power to energy storage strategies, either kinetic, potential or a combination of the two.
The point is, old notions of engines 'working too hard' are rapidly losing credence and applicability, and to a very great extent are inapplicable already. Smaller engines working 'harder' are ultimately more efficient in terms of converting fuel energy into motive force. Advances on many fronts from metallurgy (and non-metal materials science) to cooling strategies to lubricant properties and even production techniques have rendered old notions about 'working hard' vs 'longevity' completely outdated.
The features of engine design and build that bear on longevity are changing very rapidly these days. Fortunately, the process of engine development has also become much more efficient by virtue of very sophisticated computer modeling, prototyping and production techniques. That means that old notions about the 'longevity' of designs necessary to realize pay-back are also becoming dated .... no one should be surprised to find manufacturers more and more willing and able to 'abandon' designs more quickly than in the past in order to take advantage of rapid advances in technology, particularly as it relates to end-product operating efficiency.
I'm not suggesting that the current 1.6 EcoBoost is a miracle engine or a be-all-end-all. Nor am I suggesting that any specific implementation or model-run is without problems. I am suggesting that it is a significantly advanced engine design in comparison to many of the other current production engines, even those offered by Ford (2.5 non-EcoBoost) and certainly more advanced than even recent earlier engines. IMHO there is no basis for drawing conclusions or making predictions about it's "longevity" based on comparison to those 'old' technologies and notions tied to those technologies .... it is different enough that it will have to prove its own record, and in so doing will likely shatter more of the entrenched ideas about 'small engines working harder'.
When I was born Ford was still producing the long-lived flathead V8 and those confounded complex OHV engines were still earning 'credibility'. IMHO we are now in an era of more rapid and radical positive advances in vehicle internal combustion gasoline engines than ever in my life. We 'olde skoolers' are going to have to let go of a lot of 'olde notions' lest we be left behind in a could of dust ('cause these newfangled engines sure aren't gonna bury us in a cloud of smoke ;-)
of displacement as it is of the amount of available torque without the use of the turbo and when it is available.
If we really wanted to go back in time we could also have the debate over whether a low rev V8 was better than a high rev 4 cylinder for day to day use, but I stand by my assertion that the Escape maxes out the current Zetec 1.6L. If this was not the case, we wouldn't be seeing the number of recalls that are basically for overheating (remember the nice 90 part one that included cutting out 2 of the active grill shutters) and that the heads if cracked are not available from Ford, the only option for the dealer is a long block.
To me this represents either a quality control problem or a case of the engineering team performing very, very badly and delivering a solution that was one of a light duty part in a medium duty application.
And having said all of this, the 3 cylinder 1.5L when and if it ever hits the Escape may not have any problems at all, something I would expect since it's derived from the same Duratec family as the current 2.5L and 2.0L (both EcoBoost and non-Ecoboost), 2.3L EcoBoost (in the MK-C) and the 3.5L EcoBoost.