I invision a future that online wallet services will be bonded, insured and interconnected; and thus be able to provide for near-instant transfers to 98+% of the bitcoin users regardless of which wallet service that they use. I don't regard this to be equal to wallet services becoming banks, even though this kind of interconnected distance transfer service is a large part of what we commonly think of what a bank does today. That is not to say that wallet services cannot become true banks, or that a bank cannot offer a wallet service, but they are not equivilant. I honestly don't have any idea if, or how much, a future user of wallet services would be willing to pay as a monthly service fee for this kind of service, which isn't much of an upgrade from what the client can already do. The only way I can foresee such pay-to-play services becoming common among bitcoin users is if the transaction traffic were to increase to such a degree that a standard blockchain transaction were to become so expensive as to justify a parrallel/overlay network of major wallet service users that can save users' money by avoiding blockchain transactions altogether. Such a parrallel/overlay netowrk is not simply likley, it's already occuring, as that is what Stratum does. But again, Stratum is a free client that anyone can use, so I don't know how profitable such wallet services could ever realisticly become.