I believe your status is captured when you book the reservation, so even if your new status does post on line I don't think the hotel is going to see it at check in. If the property were located in the states I would tell you to call the hotel once the status is reflected on line and notify them of the status change, but since this is AMS you may want to email them instead.

You will receive access to lounge as a Gold. A room upgrade is going to be up to the property and chances are 50/50 as a gold. The email notifying them of you status change and how excited you are about spending your first nights as a gold in their property may help your cause.