Imperative almost doesn't exist in modern hebrew anymore. Whenever needed, we usually just use the future form of the verb (without the pronoun). For example, the imperative form of לכתוב (to write) for a sg. m. you would be "!כתוב" (ktov!), but it's very archaic, and תכתוב (tichtov - future) is far more common. In fact, hebrew is my first language and I have no idea whats the actual imperative form of the verb "להנות". So you're right, the form is in the future but grammatically it's supposed to be imperative, with a notion of wishing.