If you plan to use Online TurboTax (web version), the 2019 online version is scheduled to start up on Wednesday, December 4, but we don't know what time of day they will throw the switch.
If you plan to prepare your 2019 return offline in the desktop software (CD/download), that has been available for a couple of weeks.
https://turbotax.intuit.com/personal-taxes/cd-download/