Auto Zeitung have published a render of the X4 in the latest issue with the announcement of the X4 officially on the road to production.
The render shows some truth, like the actual car will be heavily based on the X3 in terms of style , however the appearance will be altered to allow it to appear more modern and sportier than the X3 so the two can co-exist.
Because BMW made a signifcant effort to make the X6 very much different to drive than the X5. The X4 will follow this philosophy too. With even the X4 getting the latest incarnation of dynamic performance control.