1. The people who are possible users of something like this are already on Twitter. The target audience is not all of Facebook, so not 10x.

2. I have seen data that can be used to argue Twitter is slipping. But to claim Twitter is dying is a great exaggeration, based on data. There are perhaps cases where a company will totally mess up something and a replacement can take over, but this doesn't seem to be it.

3. Well, hard to tell. To me the geek information bubble is the conviction that Twitter is dying. Also, I think Zuckerberg is a lot more famous that you account for. But I could not find data on it.