That's the part that won't go through. They'll claim to abolish it in phases, since of course they can't go cold turkey... but once both systems are in place side-by-side, that's the way it will stay.
No one is calling for a phase in. Greenspan asked that there be a 6 months waiting period before it took effect.
The imposition of the FairTax means the end of the income tax.
Are you deliberately misrepresenting the FairTax or are you ignorant of the facts?