Serena gave birth to a daughter, Alexis Olympia Ohanian Jr., on September 1 and has previously said she plans to return to playing in 2018.
Williams' potential return to Melbourne Park would allow the American to defend the 2017 title she won while eight weeks pregnant.
Venus is in career-best form, achieving her highest ranking since January 2011 after she finished runner-up to Serena at both Wimbledon and the Australian Open.
Serena Williams and partner Alexis Ohanian attend a gala event before the birth of her daughter in May.More news: United Nations slaps port ban on ships dodging N. Korea curbs
"I can tell you that in talking to Andy, he has been training and he is preparing for having a great year in 2018", Tiley said. She now leads. It is in several months and, obviously, it will be to her to determine where she is physically.
The men's and women's singles winners will each collect four million Australian dollars (£2.4m) in 2018, up from A$3.7m in 2017, while the entire prize money pool has increased by 10% to A$55m (£32.4m). "We look forward to welcoming her and again going on that journey of breaking the all-time record for the most number of grand slams".
The women's trophy will be presented by United States great Billie Jean King, 50 years after she won her first Australian Open title.
"Venus has also had an incredible year, turning back the clock to make the second week of every major this year", Tiley said.
Australia's charge in the men's draw will be led by world No.21 Nick Kyrgios but Tiley couldn't guarantee that Bernard Tomic would get a start.