It also emerged the cause of his death on 22 July in east London has still not been determined.
Opening the inquest, senior coroner for Inner North London Mary Hassell said the full inquest would be held in front of a jury next June.
Mr Charles, 20, died after being apprehended by police in Dalston.
She added the inquest was likely to last "weeks rather than days".
The Independent Police Complaints Commission (IPCC) is investigating the circumstances in which Mr Charles died having been chased into a shop by police officers.
The coroner told Mr Charles' family: "I'm sorry that seems a long way away - it is a long way away.
"But it is my experience that when the IPCC is investigating a death like this, it's impossible to have the inquest sooner."
The police watchdog's investigation has so far shown that, after Mr Charles was detained, attempts were made to remove an object from his mouth or throat.
It was later revealed that a package removed from his throat contained a mixture of caffeine and paracetamol.
The inquest opening at Poplar Coroner's Court heard that two post-mortem examinations had been carried out  - the second on behalf of Mr Charles' family and the police.
But coroner's officer David Brereton told the hearing that "no medical cause of death has been offered at this time" as results of toxicology and other tests were pending.
He added the London Ambulance Service paramedic who took Mr Charles to hospital noted a "foreign body was found in his airway".
Mr Charles's father Esa, a great-uncle and family friends were in court for the brief hearing.
They left without saying anything although they have previously expressed concern over the "openness and transparency" of the IPCC investigation.
Separately the Met Police has released photos of three people it wants to trace following the violent clashes and criminal damage in east London which followed Mr Charles' death.
The family of Rashan Charles have been told they will have to wait until next year for a full inquest into his death to be conducted.