Some automakers call their cars by name. Others give them alphanumeric designations. The trouble with the latter is that, if you follow a formula, sooner or later the sequence is going to either run out or repeat itself. That's the issue that Peugeot is looking at with the next generation of its popular hatchback range.
The current model is called the 308, so it would follow logically that its successor be called the 309. After that the French automaker would have to either abandon the traditional _0_ naming scheme that identifies all its products (and the _00_ for minivans and crossovers) and dip into the _1_ range, but even before that comes up, Peugeot's facing the issue that it already produced a model called the 309 between 1985 and 1993.
Rather than reuse the same nameplate, sources speculate that Peugeot could go for a name designation like it did with the RCZ coupe. The formula would likely follow across the range, leaving sister-company Citroën to stick with its alphanumeric C_ and DS_ naming scheme.