Depends on whether you want 2 or 4 door.
E90 (sedan) M3 ended production in 2011
E92 (coupe) M3 will continue for a while. Will old M3 coupe disappear once new M3 sedan is available?
Based on previous posted information:
F80 (sedan) M3 is scheduled to be revealed in June 2013, probably start production as 2014 model late in 2013
F32 (coupe) non-M internet reveal in July 2013
F82 (coupe) M3 or M4 should come out a year after that