The thing about Tether is that everyone knows that the circulation of USDT and USD in storage is not at parity. What we don't know is how big the difference is. That means that the people behind Tethen can keep propping up the price of USDT until they run out of USD. When they get to the point where they are running out of USD for people looking to cash out their Tether, that's when they will collapse.

It will be a very sudden collapse. It is very ponzi-like but I don't think it will affect people as much as Bitconnect did because I cannot immagine many people actually hold Tether for long periods of time. As more exchanges come on, there will be less that adopt tether and more that just adopt USD trading.