Hartley was dropped from the England World Cup squad on Friday after he was handed a four-week ban for headbutting Saracens' Jamie George -- the latest in a long line of misdemeanours by the forward.
New Zealand-born Hartley, who has won 66 caps since his debut in 2008, has also been punished for biting, gouging, swearing at a referee, elbowing and punching during his career.
One such incident in 2013 cost Hartley a place on the victorious British and Irish Lions tour to Australia.
In December Lancaster held talks with the Northampton hooker over his disciplinary problems and has since said that even an improvement in his behaviour would not guarantee a return to the international fold.
"There is a very real possibility that Dylan could find himself out of the squad for good," Lancaster told British media.
"There are so many impressive young players in the country who are pushing their way through and the next generation of hookers are good.
"Anyone who is not selected for a playing reason or gives up the shirt for a disciplinary reason faces the possibility that they do not make it back. All the players are aware of that."
Lancaster will also be without Leicester centre Manu Tuilagi for the World Cup after he was convicted of assaulting a police officer earlier this month.
England play the Barbarians at Twickenham on Sunday.
(Reporting By Tom Hayward; editing by Justin Palmer)
