"The post ended with the hashtag, "#TheBrotherhood".
Allen averaged a team-best 3.5 assists during his junior season, but his scoring average was down more than seven points per game from his sophomore year.
While there has been no official announcement, it appears as though Duke's starting point guard will hold off on the National Basketball Association and return for at least one more season.
"I'm a firm believer that when something feels right, you go with it", Allen said.
Pence warns North Korea
Speaking to the BBC's John Sudworth in Pyongyang, he warned of an "all out war" if the U.S. took military action. His first trip to this region since his inauguration in January also includes visits to Indonesia and Australia.
Allen will try to rebuild his draft stock after a disappointing 2016-17 season.
Even so, his presence on next year's Duke team provides some needed continuity.
He also dealt with disciplinary issues when he was suspended for multiple incidents of tripping opponents on the court.
That nonconference finale in Greensboro, N.C., on December 21 became the third time Allen tripped an opponent that calendar year. "I love being a Duke student - and continuing to be part of the university culture is something I don't take for granted". Other than Allen and possibly Jackson, Duke has four other veteran scholarship players on the roster, none of whom scored a total of 40 points previous year. Guard Frank Jackson could return, although still undecided, and big man Marques Bolden will be back.