What is the difference between "few decades" and just "decades"?
"Few" is used to mean greater than one, and usually is about two or three, but it can mean any number between two and nine. So a "few decades" refers to the next two, three, four, or so on decades in the future. In contrast, if you were to just say in the next "decade", this would only mean one decade, or the next ten years. The plural, "decades", in this case would not be commonly used because it is an unspecified amount, whereas "few" allows it to be a little more specified.