Of course they can (a prolly will) use the same hero minis. But not the monsters!
I don't think anyone here suggested they would use the monsters from Descent. Maybe I skimmed a post a little too quickly, but I don't remember that. People were asking if these figures would be the same SIZE as those monsters, but not the same actual minatures. I doubt any of the monsters from Descent will reappear here, firstly as you say because it's not a game about them and secondly because the whole differently shaped bases thing would necessitate new miniatures anyway.
I suspect the only recycled miniatures will be the heroes, but their presence in the set will probably mean most of the new ones will be the same scale as those heroes and thus the same scale as Descent's monsters.
MP3 killed the radio star
Unfortunately, looking at the video preview, all the units are smaller than the descent heroes, which looks odd because the hero models are reused and tower above all the armies. : (