I don’t think you can say he was proven right. If you read the things he said about it back then you would have thought the return of the canal would have been the end of the world. Well, it’s been 30 yrs or so and nothing’s really happened. I think most would say that the fears never really played out.
The treaties led to the Noriega dictatorship and inevitably to the US invasion of Panama in 1989. The long term results are still to be seen.