Foster - tipped to be England's number one.
Sir Ferguson believes Foster can go and become England's goalkeeper now he has fully recovered from a knee operation.
Foster returned to the team ahead of schedule in March against Derby following surgery, and was impressive in the 1-0 friendly win over Orlando Pirates in South Africa on Tuesday night.
He is now expected to challenge Edwin van der Sar for the jersey in the coming season.
Ferguson said: "I still believe Ben will be England's goalkeeper for the next few years.
"We did not expect him to get fit so quickly last season and I did not include him in our European squad.
"When I saw his performance against Derby there was maybe some regret on my part.
"The ability he has he is going to be challenging for a first team place next season. That can only be good news for England.
"With an experienced goalkeeper like David James coming back in the squad it tells you there is an opportunity for someone like Ben."
Ferguson confirmed that Van der Sar would be his number one next season.
"It will be difficult for Ben only because he is in competition with one of the best goalkeepers of all time," said the United boss.
"Edwin is a man of great experience and consistency and has looked after himself so well.
"He can play until he is 40. Ben is 24, so can play for the next 14 to 15 years. There is no need for the boy to panic. His time will come."
Ferguson was pleased with the way his side applied themselves against physical opponents.
He said: "I thought we played well in the first 25 minutes but it sometimes happens to young players, they lose their concentration.
"In the second half when Wayne Rooney and Paul Scholes came on we started to get our composure back a little bit.
"But the Pirates played with fantastic aggression. They had speed up front, which caused us bother at times. We were a bit lucky we did not lose a goal."