"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
Sohail Tanvir shares his thoughts on Sharjeel’s return
Bangladesh name Russell Domingo new head coach
Ravi Shastri reappointed as India head coach
Azhar Mahmood talks about the injustice with Shinwari
Babar Azam; from the unwanted to most wanted T20 player
Salman Butt dismayed by discriminatory treatment
PCB announce itinerary for next year's England tour
Babar Azam; from the unwanted to the most wanted T20 player
Steve Smith rises to No.2 in Test rankings
A World Cup of ifs and buts