Plas Gwyn has, as you suggest, been replaced by smaller self-catering blocks. On our* penultimate, nostalgic visit, the old place was in the throes of demolition. Evidently nothing had been spent on it since the seventies, when we haunted it! The same hideous orange rags of curtains were hanging in the windows. I think that was the same day we visited Theatre Gwynedd, under notice of demolition. The kindly staff, on their last week there, allowed us into the auditorium for a few quiet minutes. It was Cinema Paradiso and The Last Picture Show rolled into one!
It is, I think, four years since our last trip, when we were able to visit the new Pont Centre. So much has changed. I suppose eventually, only the old College-on-the-Hill will remain standing as a place of pilgrimage for old alumni!
*Not the royal we. I go with my oldest and best friend, whom I met in Plas Gwyn!