It won't always be that way because tether only represents dollars and euro in crypto world, but they really aren't the fiat currencies everyone trust. For this reason, it will not hold it's value if it started collapsing on a large scale again. That large scale collapse will cause credibility crisis once again on tether. Nevertheless, I don't see how it would also be the cause for another BTC collapse.
Bitfinex, being the slippery gits they are, have already offloaded some of that backing on others. I think Bithumb agreed quite some time ago to back Tether fully for its customers no matter what happens to USDT itself.
Not just Bitfinex but all the exchanges which have tethered the price of bitcoin to their own dollar and not just to the USD. Like what cryptopia did mid last year.
Here is an article of what could happen if tether continues on just 'printing money' for these exchanges.
https://hackernoon.com/what-will-happen-when-the-shit-hits-the-fan-with-tether-f59f92fd8dcaClip of what they said about these exchanges getting in on the business of accepting tether..
TL DR
Confidence in Tether is as fragile as the plates in the picture. The cupboard door might open any moment, or stay closed for a long time.
When the market loses faith, Tethers will gradually lose a bit of value and then suddenly become worthless. (Hemingway: “How did you go bankrupt?” Two ways. Gradually, then suddenly.”) The USDTUSD exchange rate at Kraken will collapse, meaning a single Tether will buy just a few cents. (Kraken is the only exchange to offer a market for this pair.)
The phony USDT price of Bitcoin (and alts) at Exchanges using Tether will explode to ridiculously high prices. Noobs will think they are millionaires until they learn they are rich in Tethers but poor in dollars.
The genuine USD price of Bitcoin (and alts) at exchanges that have not integrated Tether will fall as experienced investors flee crypto into USD.
There will be a flight of Bitcoin from Tether-integrated exchanges to non-Tether exchanges with fiat off-ramps. Exchanges running fractional reserves will be exposed.
The Exchanges might slam the doors shut on Withdrawals.
The Exchanges own large balances of Tether (those figures include Tethers owned by their clients), especially Bittrex, Poloniex and Bitfinex, and they might become insolvent and many clients will suffer losses.
The Bitcoin market will take a massive hit. But this process will be a lancing of the boil and Bitcoin will emerge, eventually, cauterised and stronger.
Select and test your fiat off-ramp for getting fiat out of the system now, don’t wait for the crisis. Kraken is recommended for withdrawal of Euros which usually arrive in 24 hours.
How to trade this: Watch the Tether price at Kraken. Watch the Bitfinex Cold Wallet balance and flows. Watch for an emerging premium in the Bitcoin price at Tether exchanges. Watch the Bitfinex USD lending rate (is it spiking to disincentivise withdrawals?). When these indicators show the first traces of shit hitting the fan: Move BTC and Alts out of Tether exchanges if you have crypto there. Sell everything for USD. Move the fiat to your bank. Short Tether at Kraken.
Tether Exchanges refers to Bitfinex, Bittrex, Poloniex, Binance.
Non-Tether Exchanges refers to Kraken, GDAX, Gemini, Bitstamp, CEX. (Kraken trades Tether but crucially all assets are traded vs. fiat and clients can hold USD and EUR balances.)