You are right in that WBC (and the other big banks for that...

You are right in that WBC (and the other big banks for that matter) have strong balance sheets and super profits. WBC has a ~$700bn loan book and that is not going away anytime soon. So whilst there may be short term dents in profits from fines, remediation programs and margin pressures, the cash will keep rolling in the door from interest on the current loan book and some decent dividends will continue being distributed to shareholders.

My concern is on the long term growth prospects. For decades, the big 4 banks have had the cash cow mortgage market pretty much to themselves. For most people, buying a house (via a mortgage) is the biggest single investment they will make in their lifetime and having a lender in branch that they can physically speak to is the comfort/security that alot of people have needed in that process (and ongoing through the life of their mortgage). Each bank having ~1,000 branches offering this sales channel has historically been a high barrier to entry that no other entrants could match.

However, the new generations of home/mortgage buyers coming into the market have grown up with the mindset that they can do everything they need to online. They will have no qualms about buying mortgages online rather that through a physical branch channel. So more and more over time, mortgages will become more of a commodity and the branch networks that the big 4 banks are operating are going to become more of a cost burden than the high barrier to entry that they have historically been. Searching for home loans now, online lenders like Athena can offer mortgages 150 basis points less than the big banks (simply because they don't have the high fixed cost bases that the banks have), so if it becomes a simple price decision, why wouldn't the younger generations of borrowers go to online lenders like them? The Big4 know its coming and are closing branches at a pretty rapid rate, but they have a lot of work to do to redefine what their competitive advantages are to protect their current market shares.

I have no doubt WBC (as well as CBA, NAB and ANZ) will still continue to be dominant market players for decades to come and provide dividend returns to shareholders, but its inevitable that they are going start conceding market share rather than the growth that they have historically enjoyed.