Software to file 2018 returns next year (2019) will not be available until around the end of this year.
But if you are referring to the TurboTax software to file your 2017 return this year (2018), you can purchase that now. TurboTax 2017 is up to date since your 2017 return is not impacted by most of the 2018 updates.
To see which changes affect your 2017 return that you are filing this year, go here Tax Reform Changes That Impact Your 2017 Taxes
You can see changes that will affect you next year (when filing a 2018 return) here Tax Reform - We’ve Got You Covered
- 2017 Online versions - https://turbotax.intuit.com/personal-taxes/online/
- 2017 CD/Download versions - https://turbotax.intuit.com/personal-taxes/cd-download/