It's clearly a prophesy because Jesus is self-evidently talking about his future arrival (v.46). Same as many of his other illustrations relating to the masters return. He comes at a time they least expect and rewards the faithful brides, the one who used the talents, etc, etc. He is talking about his return in kingdom power.
Yes, he is only talking about individuals, not foretelling a future organisation. He leaves it open to any individual to be a faithful and discreet slave/servant. There is no predestination and nor pre-set number nor just one individual. BUT it is clearly still a class of a type! Jesus makes a clear distinction between a group who feed and a group who are fed, between appointees who receive a reward upon his future arrival and the "belongings" over whom they are appointed.
But Jesus was clearly not prophesying about a future religious institution or the WTS or GB. Ray Franz at least made a good point about that.