Is there a reason For this continuous fall in posts?
Forum posts don't depend too much on Bitcoin halving. It has some correlation but not too strong and a bigger correlation is with active campaigns and how many posts they require each week. You can see in bull run, posts can be more than in bear market but it is explained by more companies run signature campaigns in bull market.
I also believe that Chipmixers and other mixers campaign has an impact on the percentage and the diminishing numbers of bounty campaigns both in the service section and the altcoin section, we must admit it many of our members are motivated when they are incentivized to be active here in Bitcointalk
But Bitcointalk will continue to gain more visitors as there are hundreds of thousands of discussions indexed by Google as interest in topics about Bitcoin and Cryptocurrency grows Bitcoin will continue to gain organic visitors