Well, in the 4th Cormoran Strike novel, probably more character development. We could learn more about Strike's past and how it affects his current investigations. Also, his relationship with Robin might progress further, whether it's in a professional or personal way. Maybe there will be new challenges in their partnership that they need to overcome together.
Yes, there will be. J.K. Rowling has been quite engaged with this series and given its popularity, it's very likely she'll continue writing more Cormoran Strike novels.
As of now, there is no definite information regarding a new Cormoran Strike novel. The previous novels in the series have been well - received, which might suggest that there could be more in the future. But we have to consider that the author, J.K. Rowling, is involved in multiple projects. She might be exploring new ideas or working on other stories. The publishing world also plays a role. If the publishers see a high demand for a new Cormoran Strike novel and if J.K. Rowling has the time and inspiration, then it's very likely that we will see a new one. But until then, we can only wait and hope.
I don't think so. J.K. Rowling seems to be taking her time between novels in this series. And since there are no hints or news about a new one, we may have to wait a while.