Hi,
As members are telling above, the more you know in ABAP coding the BETTER..We need to have ABAP knowledge since it is always being used modelling providers such as doing lookup, creating routines which can't be handled by existing functions, formula, etc..
That's why, I think it is better to be an ABAP consultant first before shifting to BW course..
But that is an IDEAL scenario..So we need to learn through experience, asking help from our colleagues, and reading some articles related to ABAP.. 
Regards,
Loed