Will it be possible to have in a next update the number of items in search items like a category, a taxonomy, a product to know the exact number in a specific category?
Unfortunately this is not yet possible. The reason is very simple, it is a huge performance caveat. Other plugin may be able to support this, but it impacts the performance greatly, and would very likely fail at high number of posts.
We are working on possible solutions, so don’t worry, some time this is going to be added – but search performance is a very big priority, so it has to work perfectly.