I think they will, soon or late but they will. The cryptos are now moving a lot of $, and this is a great reason for banks to come in.
Where are $ now? Into exchanges.. Where will they be into the future? Probably into the bank's pockets.
Yeah you right, sooner or later the bank will definitely do that, they see that the demand for bitcoin is getting higher
and if they don't work together maybe the existence of the bank will be eroded so they will cooperate with bitcoin