Ahh, well then. You will be effected by the changes, unfortunately.
From what I can tell, RCCL hasn't officially announced where the Diamond Lounge will be held. And reviewers probably won't report on the subject until the changes go into effect on 9/1, but here's what I did learn ...
The CL overflow room was always the Dragon's Lair (?) on the Mariner so I suspect that will become the Diamond's lounge after 9/1. You will be given free wine and champagne but drinks (including beer) will be offered at 25% off. I haven't been able to figure out if the Diamond's lounge will be available every night for certain hours or only a night or two for certain hours.
However, RCCL thanks you for your continued loyalty (insert sarcasm) and hopes you'll book a suite or gain Diamond Plus status real soon.