There is no tax reform that abolishes the IRS, except in name only. Under ANY federal tax system that extracts a few Trillion out of the economy, there will be federal tax collectors no matter what name you may give to them.
But under a national sales tax the federal tax collectors would deal only with the states, who would be responsible for managing the sales tax system. There would no longer be any declaration of income with the IRS, there would no longer be any tax returns. I can't think of anything that would better reflect the President's committment to expanding liberty and freedom then to free the American people from the shackles of the IRS.