"Opening an office on Malta gives Binance several advantages. One of which is that they can start to set up a fiat-to-crypto trading pair, allowing people to purchase crypto directly with USD or the Euro. Before, people had to purchase Bitcoin from other exchanges and then move it into Binance to purchase altcoins."
Source -
http://thebitplex.com/2018/03/23/binance-malta/Assuming everything goes well, do you think this will kill coinbase or tether? Thoughts?
Nope, because they can't operate with that on US soil anyway.
It's bad for them I believe, they'll just put themselves on the crosshairs of regulators, and would probably get taxed too.