I've not been active in the OpenStack community for some time now but I wanted to give my two cents about this.

This was one of my biggest issues when first trying to get into and understand OpenStack. It's an amazing piece of software but it's completely dead on Server Fault and Stack Overflow. There's like 1 question about it per month, usually with no answers. Currently, I feel like the only way to discuss OpenStack is through IRC. But again, I'm not sure that just creating the "OpenStack Exchange" as a subforum of the Stack Exchange network would necessarily change this. Maybe it's more of an engagement issue rather than the actual platform (although I think that IRC should not be the only place for the community to be, as I perceive it to be today).

Anyway, I really hope that this changes someday and there are as many OpenStack questions in forums as there are for Ansible. :)