Or......you may be able to top it with a Self Levelling Compound. Not all Self Levelling Compounds are suiatble for a wear-surface but some are. Mapie (I think) makes a Self Levelling Compound that is intended for a wear-surface and can even be acid stained if so desired.
Just a thought.
I have used floor planers and grinders on concrete many many times over the years but they all tend to follow the existing contours. I can't imagine how tuff it would be to grind only the highs and leave the lows, just can't see how this could be cost-effective.