This "WeChat does everything" idea sounds similar to what App dot Net was trying to do. If I recall correctly, ADN was supposed to be a support layer where different things could ride atop. They built their microblogging thing and I think there were a few alpha products being built, but they ran out of funds. I think partly because their biggest product was the microblogging site, and it was mostly a smaller and paid version of #Twitter ... it is hard to gain enough paying customers for the same thing that a larger zero-price competitor offers.
So let's say Twitter goes 100% paid, will they still be the world's leading source for news and information? I cannot answer, but I don't expect to be among their customer base.