Without a clear indication of size, as no other vehicles are placed next to the prototype, we can only speculate that the Volkswagen Polo will increase in dimensions. This is an easy assumption to make, as the prototype is riding on OEM 18-inch wheels.
The model of the rim was known as “Detroit,” and it's most famous for being available with the Mk V Golf GTI. Do not confuse the “Detroit” rims with “Huffs,” as the former have pronounced black detailing inside the circles between the spokes.
Coming back to the prototype, the 18-inch wheels do not seem huge when compared to the body of the next Polo. Instead, they appear to fit the car just as well as they suited the larger body of a Mk 5 Golf. Making the Polo bigger would be a natural step for Volkswagen, as many of the cars in its segment have grown lately.
The most curious aspect of Volkswagen testing the Polo GTI is the fact that the German automaker is doing this across the Atlantic. The smallest model in the Volkswagen current lineup in the USA is the Beetle, which is the platform sibling of the Golf. However, the Beetle might be discontinued after 2018, so VW might need another model in the most affordable part of the range.
Since Volkswagen is considering the possibility of launching the Polo in the USA, the German automaker might as well introduce the GTI version on the market. There’s no official word on that matter yet, so we will just have to wait and see.