Is there a way with turbotax to estimate 2021 taxes now? I need to determine if I can stay within my tax bracket and do a Roth Conversion before year end.

Try these tools:

http://www.irs.gov/Individuals/IRS-Withholding-Calculator  

 https://turbotax.intuit.com/tax-tools  

http://turbotax.intuit.com/tax-tools/calculators/taxcaster 

Tax Bracket Calculator - 2020-2021 Tax Brackets | TurboTax® Official (intuit.com)

Even though the downloaded program comes out sometime in November each year it is only a beta version which will not be fully operational until  late January at the earliest (much later for some forms and the state programs).  Efiling will not be open until late January at best so do not be in a rush to file.

Same with the Online version which becomes functional sometime in December. 

 http://taxpreparationsoftware.com/

If you are trying to do some tax planning then use the fully operational 2020 downloaded version instead.