A reliable banking partner is prerequisite to run a fiat-crypto exchange. Loss of banking partner is fatal to an exchange, and should immediately trigger a wind-down. On the flip-side, the banking partner should in good faith, continue to process withdrawals until the wind-down is complete. Bitfinex's refusal to wind-down after the Wells Fargo decision is irresponsible. Wells Fargo's decision to immediately stop processing withdrawals without a grace period is bad faith.
Reliable banking relationships are difficult to maintain if you are not in the same jurisdiction with said bank. If you want to process USD, you have to be in the US. Multiple fiat-currency crypto exchanges are not sustainable due to this dynamic.
I see a sustainable status-quo as fiat-exchanges becoming single-jurisdiction, single fiat-base. Ironically, just like most banks.