How much will I owe if I file a 2019 tax return for next year

No one can answer that.  We do not know how much tax due you have for the 2019 return or even if you will owe.  We cannot see your information.

If you are getting a refund, there is not a penalty for filing past the deadline.  If you owe taxes, the interest/penalties will be calculated by the IRS based on how much you owe and when they receive your return and payment. The IRS will bill you for this; it will not be calculated by TurboTax.

If you do owe for 2019 and wait until next year to file the return you will be subject to failure to file penalties and interest on the amount owed---but again, only the IRS will calculate the amount.

FYI ... efiling a 2019 return will close on 10/15/2020 ... after that you will need to mail in  a paper return AND if you have not completed the return you will also need to switch to the Downloaded version since the ONLINE version will also close by 10/20/2020.