I feel like almost every car has issues that are eventually corrected in subsequent model years. I personally wouldn't want to pick up the first couple years of production of the new M4, so now you're looking at having to wait several years. I say get the M3 now and then a few years down the road you can think about switching into the M4 (if it ends up being good!).
//'04 330i ZHP (gone) //'07 E92 335i (gone)//'08 SG E93 M3 (gone)
//'11 Z4 sDrive35i (gone)//'11 Jet Black E92 M3 (gone)
//'11 Carrera GTS