If you have to pay more medicare payments due to increased income they use the 2017 return AGI for the 2019 cost not the 2018 ... they use 2018 for the 2020 ... so you don't need to estimate anything ... you will have a complete return to use in time for the change.
2018 form 1040ES forms are included in the 2017 tax program, 2019 in the 2018 program and so forth.
