I don't remember Bungie ever admitting to not wanting to make more sic-fi games, I only remember them saying they wanted to try something different from what their Halo games were. So yes, while Halo is a sic-fi game, the genre itself is massive and is probably one of the better genre types that will allow them to bring their new game Destiny into a "new and different direction" as opposed to their Halo universe.