If TNG expected us to believe that BOBW was the end of the Borg threat, then they really either think we're idiots or they needed to work harder. Because BOBW really just left us with a "Great, they just barely beat back ONE attack. What now?"
TNG did an epic story where Earth and all of humanity was nearly destroyed, there was no way for VOY to top that because they were in the DQ. No one would give a damn about VOY doing anything to save the inhabitants of the DQ from the Borg, meaning they had no chance of doing a story equal to BOBW.
TNG said they came from the Delta Quadrant in "Descent". So by DS9 season 2 they did know.