Given an option on an underlying future, where the option matures at $T_1$ and the future matures at $T_2$, and $T_2 > T_1$, when priced using the Black76 formula, what is $F$?
Is it just the current futures price $F(T_2)$? Or do we need to compute some sort of estimate of what the futures price $F(T_2)$ is seen from point $T_1$? And if so, how do we do that?