Gen 1 had a MCA (mid-cycle action) for MY16, when it gained the Mazda Connect system. Mazda seems fond of small MCAs in general, so I could see the recent additions for MY19 being all we're going to get until the next-generation model.
Gen3 could land as early as MY21, if the current model is as short-lived as the original. Assuming that Mazda can get Skyactiv-X into mass-production, I could definitely see them wanting to get that engine--and the other platform/electronic improvements that debut in the MY19 Mazda3--into the CX-5 sooner rather than later.
Not quite. Model years didn't match up with real years for Gen 1.
Gen 1 (2013 MY) was in 2012. Gen 2 caught up to actual year at 2017. I think Gen 2 will hit a refresh before we see a Gen 3 personally. Gen 3 might be the Skyactiv X engines? Seeing the new 3 isn't even launching with that yet, I think it'll be a while.