- Are there any plans in future developments to add private topics & replies ?

It's already available, you should manage Forum permissions in Forum settings for certain Usergroups.

May be helpful: https://wordpress.org/support/topic/how-to-restrict-part-of-the-forum-to-some-users?replies=2#post-8689925

- Will you add the ability to manage "categories" of topics with specific labels (Support needed, Resolved etc ) ?

Forums labels in near feature. But for topics have already  icons. The solved is only for Q&A Layout.

- Are there plans to add more advanced support features: have the possibility to create and assign staff-agents to some topics for exemple ?

No yet.

- Do you plan to integrate canned-replies in the future ?

I'm sorry but I didn't follow you.

I installed the WPFORO Forum plugin to see how it works and I was very pleasantly impressed and surprised.

I usually use bbPress with differents addons. My test-migration was very simple.

Actually, there are features that would miss me for WPFORO to be perfect for my own usage:

- Are there any plans in future developments to add private topics & replies ?

- Will you add the ability to manage "categories" of topics with specific labels (Support needed, Resolved etc ) ?

- Are there plans to add more advanced support features: have the possibility to create and assign staff-agents to some topics for exemple ?

- Do you plan to integrate canned-replies in the future ?

Thanks