As a general "rule of thumb", stroke symptoms continue to improve, slowly, until about 6 months after the stroke. Therefore, there are still several months left for him to get
However, what is never clear, is the degree of expected improvement. I frequently tell people that forecasting recovery after a stroke is a very imperfect science - not unlike asking a weatherman what the weather will be like in a week, or asking an economist what the economy will look like in six months. We simply do not have good forecasting models to answer these questions. The best way to estimate his future progress is to see how far he has come already, and expect this progress to continue at about that same pace, with some slowing down of improvement, for the next few months.
Therefore, unfortunately, there is no way to give you a straightforward answer as to whether or not his delusions will stop. Delusions are quite common after a stroke, and in many cases go away.
As a final thought, I would make sure that he does not have another reason for the delusions, such as day/night confusion in his room (like keeping the windows closed at all hours), or the effect of new medicines that were started during his hospitalization.