It's not a matter of tax rate predictions; it's purely a matter of the total amount of tax payments over the remaining years of one's life. I'd rather pay a one-time conversion tax on, say, a $600k valuation than pay income taxes each year on withdraws and Required Minimum Distributions of 6%+ on $10M or more in a Traditional IRA. (assuming Anavex reaches a valuation of at least $4B, which shouldn't be a problem)