4 series should start soon at least the coupe. I've seen BMW start production at strange times but the X1 change really is strange. Must be totally related to the other vehicles in the same factory the X1 comes out of so they can stagger the changes in the production change overs. If the 4 series or wagon come out of that factory it could be related to those.
1995 325i,1996 328ci,1997 528i,1997 Z3 2.8,
2001 X5 3.0,2001 330i Conv,2002 M3 Conv,
2003 M3 Coupe,2004 M3 Coupe,2004 Z4 3.0,
2004 X3 3.0,2007 X3 3.0,2007 335i Conv.,
2013 X1 28 sdrive M Sport, 2014 M235 on order