I'll raise the issue around better support for tasks/project related items, but in the mean time..I haven't seen anyone do anything Gantt related in a long time. I've seen more people asking for Trello/Workfront here If you could build a "quick activity integration" in 5 minutes, what technologies would you look to integrate first? ... where it would pretty simple to do a Simple Stream Integration or Tile perhaps to expose their constructs in Jive.
Closest I saw (that is public) was a long time ago in my SBS Widget Pack - Plugin which has long gone the way of unsupported. Perhaps someone else will have something to share?