I released a paper earlier this year talking about how we can reasonably lock cryptocurrency to fiat, but unfortunately the space is still rather immature. A single provider of USD tokens is extremely dangerous. Best case scenario would be if there were many companies like Tether and you could spread your token purchases between them automatically to minimize counterparty risk. Stellar and Ripple are closest to solving this since they have fiat trading pairs for each trusted exchange on their network. In the future that could mean issuance from hundreds of banks.

Here is the paper if anyone is interested: https://www.gogreenmango.com/whitepapers/Bitcoin-Volatility-...