Ecoboost goes back to the days when Derrick Kuzak was product chief. They did very well with the products developed under his watch. With skyrocketing fuel prices and increasingly stringent emissions regulations, they were concerned with utilizing technology that addressed both of those issues while providing superior drivability to a larger NA engine at a premium that could be recouped quickly by the consumer. That's why Kuzak, who was in charge of product development around the globe, decided to stick to GTDI in the U.S while having a roster of diesel products elsewhere. That ended up being fortuitous because with the flip in diesel prices now it takes much longer for diesel to pay off. Longer than most consumers will do the math for.
They also could use the formula across the entire product line, from tiny little Fiestas all the way to full size trucks, and could bill the product as a bonus based on fuel economy and performance. Hence the whole TwinForce vs. EcoBoost thing. It had a catchy performance name even though it was primarily developed for fuel economy/emissions. Obviously it's worked because they've sold over 500,000 of the F-150 versions alone. While they could really make a GTDI version of anything in the lineup, in my view, the prospects of a 5.0L DI Ecoboost motor ever going in anything are extremely dim until it appears in an F-Series pickup to justify the expense.
It's a great thing for Ford Performance enthusiasts that Kuzak's replacement, Raj Nair, is a certifiable performance nut. He owns a Tungsten, Ford GT 2006 #0001, and will be at Rally 10.