Auto manufacturers are in business to do one thing... make money right? In order for them to do that, they must provide a product that consumers will buy. Forecasting what that product is going to be several years down the road is tough. Personally, back in 2010 I thought the car future was going to be CUV and small cars. Well, here it is in 2017 and bigger is better...again. Fuel costs play a major role in this development and there is no shortage of fuel at a low cost. In addition the political climate is such that, at least for the foreseeable future, vehicles like the 4Runner will continue to enjoy a big demand.
Look at what the other guys are doing. Ford is bringing back a BOF Bronco and bringing the Ranger back too. Both are inefficient compared to a Focus but...big deal. GM is tricking out their twin pickups and rumored to build a BOF SUV on that platform as well.
On the home front, the 4Runner is selling record numbers even though it is seven years old. Right now, people want these vehicles. Sure, CUV's are popular (Honda CRV sold 357K last year) but so are the BOF Jeeps too. Jeep is coming out with a truck next year!
Bottom line, the 4Runner and vehicles like it are in demand for the next several years. I agree that Toyota was caught with their pants down with regards to 4Runner development but, like any good company, they will change it up and offer a 6th gen in the next few years. It's what their customers want.