When approaching to land, I don't think I've ever been told to maintain an altitude without being given a reason why and a point at which I can descend. As controllers like to say, "We haven't left one up there yet."
I don't think ATC is authorized to tell an aircraft operating on an IFR clearance to "remain clear of class bravo." They can cancel the visual approach clearance, but they would then have to provide an alternate clearance to the destination or else a hold with an expected further routing.
