The 'logical' place for TurboTax to ask about estimated taxes is where a typical person would think of it. That is after finishing the taxes and ready to file.
When TurboTax gets to the place to finally file your taxes (whether efile or print), TurboTax should ask the user 'do you want to calculate your estimated taxes for next year?'. That's the logical next step.
Also, it should not be hidden in the topic list but written as its own category 'ESTIMATED TAXES' in the section about final steps.
My 2 cents.
