However, let me now say that there SHOULD be a Mazda CX-6,
During the Regal TourX launch, Buick's product planning folks pointed out that such a crossover wagon (let's go with that term for now) filled a market niche that's really not being satisfied. One that's more stylish and luxurious than a Subaru Outback, but more functional and less expensive than an Audi Allroad. It would cater to people who seek something different from the norm, both in terms of brand and body style. Sure, it's certainly not a big market niche, but it is seemingly growing.
Well, if Buick is indeed onto something and that growth continues, then Mazda could most definitely go after that same market niche. Sure, it's a small niche, but all three Mazda6 generations have sold in such minuscule numbers (33,402 in 2017), why not try something completely different? I could easily see a CX-6 outselling its sedan sibling. Such a Mazda crossover wagon would only have a Buick and Subaru as competition, as opposed to trying to draw customers away from the Honda Accord, Toyota Camry and every other midsize sedan at a time when the entire segment is hemorrhaging sales. It would also nicely complement a lineup of crossovers that includes the CX-3, CX-5 and CX-9, providing yet another alternative to entice customers.