Big banks are already looking seriously into cryptocurrencies. Like seriously.
Cryptocurrency uses blockchain but blockchain isn't cryptocurrency.
Blockchain technology is already incredibly useful for banks doing interbank currency trading iirc.
I guess you could be talking about banks doing crypto trading, then I would guess that they are but a number are still stuck in the stone ages.
I wish people in this entire thread weren't allergic to providing citations and references though.
A settlement blockchain between financial organizations doesn't have the same design parameters, and could conceivably run larger blocks, shorter block times, or not store block history at all but rather reach consensus on state (which is what Ripple does)
Calm down