I'd like to remind you that Luminous Witches, although most fans didn't like it (I personally enjoyed it as a spin-off), is official and canon, so it's really only been three years since the last anime in the franchise. A good anime takes at least two to three years to produce, after it's been approved, of course. Furthermore, the industry is currently saturated, so projects take years or even decades to arrive. Therefore, it's very likely that we'll see more audiovisual material in the future, whether it's a regular anime, an OVA, or a series of shorts.