Unless it's a huge change - Standard room to a four room suite for example, if they don't mention it and you don't ask, in many cases you do not know.

Part of the problem is defining upgrade. Is it simply moving across the hall to the same room just with a better view? Moving you away from the ice machine to the same room down the hall?

But it's one of the issues with Hilton (though in no way unique to them) an upgrade can be not all that much different from the room you were in.

Unless it's one of those big changes, it really doesn't matter all that much to me if there's an upgrade or not.