Or people will accept it as paper dollars and carry on regardless. Honestly this wouldn't surprise me - it'll just be a representation of the dollar that things use as an intermediary step.
Well, if Tether isn't backed by dollars, then there's some pretty big questions to answer - for example: "When people buy tether using fiat currency, they hand $1 to bitfinex, and in return get 1USDT. Where did that real $1 go?"