I don't think topics can be exhausted, on a daily basis there are new development coming up on bitcoin and cryptocurrency in general so people will definitely have something to post about, even currently that you think there is topic there are still lot's of shit posters so I don't believe getting out of topic is the cause of shit posts.
I Believe that they will no be elimination of shit post provided that the community is concern, but we have to understand that shit post doesn't come by creating thread, i can say were we can notice a shit post through respond or comments in a thread. So in the aspect creating of topics, i have portray my points before because concerning this, but let me use opportunity and repeat it a little bit, the more we are getting older here the more new people will come up with new ideas of cryptocurrency topics through a research that will be profitable to the society at large. So this is my personal opinion but i dont know for others.