A few years ago, I was having a water-cooler conversation with a colleague, who made an offhand observation that crossovers were getting so prevalent, he wondered "could crossovers ever replace cars?" Now, let's unpack that statement a bit, since there are multiple levels of meaning and interpretation to it, the answers to some of which would be a qualified "yes" or decisive "no." But what seemed a ridiculous statement or hypothesis a few years ago is now looking surprisingly prescient.

The broadest definition of "car" includes anything that you can legally drive with a Class C driver's license, which would include pickups, SUVs, sedans, coupes, sports cars, moving vans, and most RVs. Strictly speaking, the generally agreed-upon dividing line between "car" and "trucks is whether it has a separate cargo bed and, in the case of an SUV, whether it's body-on-frame or unibody. Trying to slice the pie into thinner slivers results in a jumbled mess of conflicting and sometimes contradictory definitions and examples.

Case in point: Have you ever once heard the Jeep Grand Cherokee referred to as a "crossover"? I haven't. In its entire 20-year existence, I've only ever heard the Grand Cherokee referred to as an SUV. Yet for its entire existence, the Grand Cherokee has been unibody, just as the original XJ Cherokee compact SUV before it. Yet the Mercedes-Benz ML, with which the current WK2 Grand Cherokee shares a significant deal of its engineering and hardware, is sometimes referred to as a crossover, though its fundamental architecture and layout are essentially identical to the Jeep's. What makes the difference? Is it that Jeep is the definitive, original SUV brand and Mercedes-Benz is an upscale maker of European luxury cars?

Vehicles like the current-generation D4 Ford Explorer, related Ford Flex, and 2013 Nissan Pathfinder and Infiniti JX35 (now QX60) are generally considered crossovers. Their transverse powertrains and unibody, car-based chassis make for a fairly easy definition.

Things get hazier still when you start looking at vehicles like the Subaru Outback, which by external appearances looks like a high-riding station wagon. Yet it was awarded our 2010 SUV of the Year award. The Audi A4 Allroad, also for all intents and purposes, is a wagon, but was honorarily included in this year's SUV of the Year testing, presumably on its conceptual similarity to the Outback.

Looking at developments within the industry on a global level, far and away the segment getting the most attention is crossovers. And not just in the upper echelons of luxury brands. From the B-segment upward, manufacturers are falling over themselves rushing to get new crossovers into showrooms from Mumbai to Manhattan.

While it's unlikely crossovers will ever fully replace conventional cars, the trend of cars starting to adopt crossover-like traits is already beginning to be seen in concept cars, and in some cases, production vehicles as well. The European version of the 2014 Kia Soul (which itself blurs the line between car and crossover) is getting a few rugged-looking styling details to give it a somewhat more truckish appearance.

At this year's Frankfurt motor show, witness the Audi Nanuk concept, which at first glance, is a sports car in the vein of the R8, until you look at its elevated ground clearance, angular styling, and hefty 4200-pound weight.

I personally don't envision the Corvette getting 70-series tires and 9-inch ground clearance or the Ford Fusion suddenly getting knobby tires and a front winch. But the influence the crossover trend is exerting on the broader automotive industry is undeniable. Could the day come when the majority of car models on the market exhibit some attributes of crossovers? I'd say the answer to that question is a definite yes, if we're not there already. Joel, forgive me if I snickered at you. You hit the nail on the head.