This is why any change to a new system needs to be explicitly tied to the repeal of the 16th Amendment via a new amendment that outright forbids any return of the income tax.
Most people who have read the bill or looked into it via the FairTax website know that the income tax (and some other taxes) and the IRS are eliminated when the FairTax becomes law. In addition the income tax records are required to be destroyed and the 16th amendment is identified for repeal since it cannot be repealed by a tax law. A Constitutional amdndment has different requirements than a tax bill.
Removing the 16th, however, is very much the aim of the FairTax backers and once here is a workable tax law in place the repeal of the 16th becomes relatively easy since it serves no p[urpose - much like the prohibition amendment it is an anachronism.
In the meantime though, the FairTax will eliminate the income tax, the IRS and the income tax records. Restarting income tax again is no snap of the fingers task and would be impossible since if there is enough backing to pass the FairTax, there's enough backing to shoot down any new attempt at turning back the clock to an income tax.