Wildly speculative. Turkey is predicted to have 9.1 [some unit], while Germany 6.8 [some unit]. There are two countries with similar demographic profiles, with Germany having 5x the [nominal] GDP of Turkey today. Short of nuclear war or an asteroid landing in Ruhrgebiet, it's hard to imagine what would lead to Turkey's economy overtaking Germany's in 11 years.

PS. "nominal GDP using purchasing power parity exchange rates" is nonsense. Not sure if the error lies with the journalist or with the source.