Take, for example, the Volkswagen Up! supermini currently offered overseas in three- and five-door bodystyles. It may be the size of an earlier Polo, but it's smaller than the current one. But even that is apparently destined to get bigger, too.
According to Autocar, Volkswagen is developing a longer-wheelbase version of the Up! for specific markets. We don't know which markets those are, but the Up! and its derivatives aren't sold in the US, and it apparently isn't destined for Europe or – contrary to what you might think – China, either.
As with most stretch jobs, the longer wheelbase is expected to benefit rear-seat legroom. Considering that Skoda tends to offer lengthened versions of VW models, we wouldn't be surprised to see the stretch being applied to its Citigo twin, too.