Mazda is looking to replace the Mazda CX-5 soon and from what we have seen and heard, it looks like Mazda CX-5 will not be straying too far from the actual model or it least that seems to be the case.
Based on the spy images, it looks like the Mazda CX-5 will come with the same measurement which made sense since they did make the CX-9 smaller. A larger CX-5 could bring the two too close. They made some changes to the grille and as well as the headlights and taillights as well.
One of the issue that the Mazda CX-5 owners seem to have with the current model is its gutless drive. That problem could be solved if Mazda does decide to fit in the new Mazda CX-9 engine into the upcoming 2018 Mazda CX-5.
According to Mazda, the new engine was made to fit into the other Mazda model so would fit but whether Mazda will be offering it or not is a whole other story.