IANABE (I am not a banana expert) but I know that no one suggested there is a shortage right now. What's threatened is the world's supply of Cavendish bananas which is what every Western country imports. Prior to that everyone ate Gros Michel bananas, but practically all plantations growing that particular crop were wiped out in the space of 30 years by Panama Disease. Cavendish was the response - it was Panama Disease resistant, but about 15 years ago the disease started attacking Cavendish crops. The concern is that this means we're a decade or two away from losing Cavendish and we don't have a suitable replacement (because, as people have said in this thread, other bananas aren't as tasty to Western palettes).
To post "Nah, there's no problem" shows you don't quite understand that problem, and to cite that you've seen a few big banana plantations as evidence that the problem isn't a real one just compounds the issue.
If Panama Disease mutates to attack the plantations you saw they could all be gone in a decade. That's how virulent the disease is. It is a problem.