Dembele has been eyed by Barca since Neymar completed his world-record €222 million switch to Paris Saint-Germain last week.
The 20-year-old missed training without permission on Thursday, with Dortmund head coach Bosz telling a news conference the club had been unable to contact Dembele.
The player was subsequently suspended until after Saturday's match away to Rielasingen-Arlen in the DFB-Pokal.
And Bosz has revealed Dembele's future should be clearer by Sunday, when the club will provide an update after holding talks to decide their next move when their cup tie is over.
"We will sit down and talk this evening," Bosz told Sky ahead of kick-off.
"Tomorrow [Sunday] morning the club will communicate what we will do."
Dembele scored 10 goals and supplied 21 assists in 49 games for Dortmund in his debut season with the club, having signed from Rennes for €15m last year.
BVB chief executive Hans-Joachim Watzke has suggested a fee of €100m for the player is "in every case, not enough".