Glad you asked, and I am with you 100% on totally ignoring any stunt that gnome BM comes up with.
I just see the 9-9-9 plan as something that switches the debate from “let’s lower the cost, size, and intrusion of the Federal Government”, to “how do we collect the money the Federal Government requires of the people to at least maintain its present scope and role in society.”
And, addind a balanced budget amendment to the 9-9-9 would not help, because the sales or VAT tax part of it hides the amount of money it extracts from you. How? Easy - the sales tax is not charged at point of sale, it it collected from the business on their Schedule C or Federal Corporate Income Tax Form (in addition to the 9% corporate tax), and the whole plan does nothing to get rid of the worry of trying to comply with the tax code, filing forms, hiring accountants and tax attorneys, audits, collections etc. So what if it gets rid of a few deductions to calculate and loopholes for some - others are written and quickly take their place (see 1986 tax reform).
There is so much wrong with it, I could not possible list them here right now - my main point is - it changes our focus from the real problem: Federal Government size and over-spending, to how do we extract the money from you!
You can't "guarantee" anything in politics. Cain does not know what the composition of Congress will be if he is elected POTUS.
However, his plan clearly states that 9-9-9 is a first step towards the Fair Tax. A Fair Tax is what conservatives have been dreaming for decades.
Cain also wants the Balanced Budget Amendment with this. This will limit gov't spending to a percentage of GDP. Cain also includes a provision that tax increases must be with a 2/3 majority while tax decreases can be done with a simple majority.
There is not one person who can look at 9-9-9 and say it is inferior to our current, corrupt, IRS-laden tax system.