"I'm contracted to September 2019 and that will see me out," he told the BBC.
England finished at 180 for nine off 88.1 overs as Australia won by an innings and 123 runs.
All four of Australia's front-line bowlers finished with 20 or more wickets each for the series.
Usman Khawaja plundered a big century as Australia roasted England's bowlers on Saturday to open up a 133-run lead with two days to play
At the close, Smith was on 44 with Khawaja reaching his highest score of the series on 91 in Australia's 193 for two
Skipper Root again missed out on an elusive first century in the series as Aussies struck late on the opening day of last Test
Root and Malan stole the highlights on the opening day of the SCG Test
Woakes has taken 10 wickets at 49.5 in the four Tests and scored just 114 runs through seven innings batting number eight at an average of 16.28.
Left-armer Starc is the leading wicket-taker in the series with 19 despite only playing three Tests
Fawad Alam in line for a Test comeback?
Sindh claim victory in last-over thriller after Babar Azam ton
Imran Nazir excited for Qalandars High-Performance Center
Shehzad ton overpowers Asif's cameo as Central Punjab edge Northern
Sarfaraz, Rizwan urge fans to throng the Iqbal Stadium
Virat Kohli floors South Africa with career-best double century
Tanvir Ahmed blasts on PCB for shutting departmental cricket
Kohli within touching distance of replacing Smith as No. 1 Test batsman
Zimbabwe readmitted as ICC member after three-month suspension
Babar adds one more record in his inventory