current Z4Automobile magazine has tweeted a report that the next Z4 will be coming with a turbocharged four-cylinder in the base-model, replacing the naturally aspirated 3.0 liter inline 6-cylinder.
BMW has been rumored to be developing a new 2.0 liter turbocharged four-cylinder petrol engine to fit into its lineup for quite a while. It's difficult to speculate to what power levels the new power plant will be configured, but if it is to replace the existing 255bhp 3.0 liter inline 6 in the sDrive30i, then a comparable output level is to be expected.
BMW has no force-fed 4-cylinder petrol power plants in its lineup before and has historically favored naturally aspirated engines. However, advances in turbo technology plus growing emission restrictions has changed that equation and it only seems inevitable that BMW would go down that route. Never say never!
Such a move would also make the Z4 more marketable in countries with a road tax system like Singapore.