There are no plans to do so, and I highly doubt they will.

For one thing, not only does VII have the larger fan base, it also grossed far more money than VIII did. That makes expanding it to be a generally safe venture.

Also, there's nothing left to do with VIII, at least not with the main characters. Where is their room for a sequel? VII left it very vague and very open, so there are countless things they can do with it. VIII wrapped it up neatly and that was that.

The chances of a sequel of any kind for VIII are slim to none, so dont get your hopes up.