By Stephen Edelstein

BMW’s takeaway from its sports-car collaboration with Toyota is supposed to be the next-generation Z4, but a new report suggests that model may not arrive for quite awhile.

BMW hopes to launch a new Z4 before the end of the decade, but the model isn’t a priority right now, Klaus Froehlich, the company’s chief engineer, told Automotive News Europe (subscription required) at the recent Geneva Motor Show.

The market for two-seat luxury convertibles is shrinking, so BMW thinks the current Z4 – which launched in 2009 – can hang on until 2020, even though it will have been on the market for a decade by then.

The roadster’s fall from grace was also partly the impetus for teaming up with Toyota. The program will lower development costs, helping BMW make up for lower sales volumes.

Helping to convince officials of this strategy is the fact that roadsters like the Z4 don’t sell well in the world’s largest car market, China.

Drivers there reportedly prefer bigger, fixed-roofed cars that convey a sense of privacy. The country’s legendarily bad air quality also makes driving with the top down problematic.

Given all of that dour analysis, it’s probably lucky that BMW is planning to build a new Z4 at all.

It’s unclear how all of this will affect Toyota’s launch plans for its sports car, which is widely to believed to be a spiritual successor to the Supra with styling modeled on the FT-1 concept from the 2014 Detroit Auto Show.

Each company will probably follow its own timetable, so it’s possibly we’ll see the Toyota sports car at some earlier date than the Z4.