That sounds like a reasonable conclusion. Libra will probably be superior to any of those alternatives, which means their use will go down. What will happen to the price of Bitcoin is an interesting thing to consider. I suspect unbacked USDT has been used to buy Bitcoin and if USDT were to lose demand, that would force Tether to use its reserves to redeem USDT. But even if adequate fiat reserves were missing Tether (owned by the same people as Bitfinex) could cash out their BTC reserves to pay for the redemptions. On the other hand, major internet companies going crypto will lend credibility to the whole space and may boost BTC and alt valuations.