Probably mid/late Nov from previous experience but don't count on it being fully functional not the least because tax logic and the forms cannot be finalized until the IRS and states get their forms and instructions done, which would not be until early next year.

In the meantime, you can test some of the new features that Intuit may roll out but definitely do not try to rollover live returns to next year until later next year unless you don't mind doing the proforma again and fixing errors that may pop up or omissions when you work on those returns.