I doubt it is possible because crypto is a volatile asset, so they can't give a valuation to it and provide interests for saving crypto in their account just like what we do with our bank accounts and other other reason is it is not controlled unlike fiat so they can't print more money and circulate their deposits via loans and others like they usually do with our fiat deposits. It's simply too much risk for them.

Possible ways, the banking industry can enter into the crypto field:

1. Provide buy/sell/swap service -  which is very much possible and it can bring immediate customers to them but they may need different licensing to do the exchanghe service but it will be worth it.

2. Payment processing - (it comes under the swap service, though), there's a potential to fill in, if they manage to bridge the crypto buyers and fiat vendors.