Will this screw up when the earths field begins fluctuating when poles being going into reversal again?
Seeing as the force generated is in a direction perpendicular to both the satellite's direction and the magnetic field lines, it really shouldn't have a major effect.
As long as the magnetic field stays at least somewhat parallel to the earth's surface, a lift force will be generated regardless of the field polarity.
Of course, if there is zero magnetic field that means no lift force, but that doesn't mean things immediately fall out of the sky, only the potential to drop a little in orbit until the field picks up again.
