We have a website which receives 20K-30K unique visitors every day (100 live users at any given time) It is hosted on a HostGator shared server. We have never had any serious problems these two years and the admins are extremely useful and friendly.
We have decided to create a subdomain on our site where the forum based on XenForo will be, like forum.site.com.
During the first months, we do not expect to get more than a few thousands posts and we expect the peak of users at the same time to be around 30. Will the shared server be enough?
Of course, if the forum increases we will update to a VPS, but for the moment we do not want to update.