Banks may well adopt blockchain tech for their own purposes, but they aren't going to create anything like bitcoin. Anything they use a blockchain for will be completely centralized and against the spirit of other cryptocurrencies like bitcoin. They probably won't even create any coin at all but simply use the distributed ledger aspect for bookkeeping purposes and they might employ smart contracts too.
And let them do it. I'm all for it, but nobody ought to think that anything the banks do will be in competition with bitcoin, because it won't. Blockchain tech and bitcoin are related but separate things when it comes to the banking system.
Of course, when a particular bank is creating their own coin, it is completely centralized.
That's how they can fully control its distribution.
But the thought that banks are creating their own crypto coin, means a lot already.
It translates to the fact that they do believe the advantages of blockchain technology to improve their system.