Should I sell my new G3 and buy OMD 5 or EPM2 later when the prices drop?

RTFM!!  Before you go out and change cameras, just go out and shoot pictures! Learn about white balance settiings!  Unless you're a pro photographer with very speciific needs, (studio, sports), if you can't take good pictures with the G3, you won't be able to do much better with the others. If, after all that, you still feel the G3 doesn't meet your needs, then go for it and pay double the price ...