I think Dr. Keyes has had enough of a history in arguing for lower taxes that I can safely say that his ultimate goal is lower tax burden for everyone, not just the black community.
In as much as strategically he feels getting it lowered for this particular group is an effective way to break the Democratic coalition, which paves the way to that ultimate goal, I think he may be onto something.
Problem is if this were to go into place it would be a huge rallying cry against future tax cuts (and even more so against tax irradication) until the grace period is over. Anytime during this grace period when taxes gets lowered would be effectively lowering the value of the reperations, lowering our concept of guilt over slavery. This could turn into the ultimate weapon against tax cuts.
Then there's still the problem with how many blacks live below the poverty line (more than any other minority), none of them will gain any benefit from this because they already don't pay taxes. It's easily argued that these are the people owed the most (because they've had such a hard time oercoming the "obstacles" of slavery) and they wouldn't benefit at all.
All around a bad plan that doesn't do an adequate job of addressing the heart of the reperations argument or offer any tool to use against our abusive tax system.