Rather the opposite. They can handle all the small transactions if they can do it better, in the market, then they can clear out in bitcoins. Off chain transactions.
Anyway, the intrinsic payment system in bitcoin is not that bad, if you discount the future changes. Remember, an international credit card transaction might include ten institutions, each having their own system, backup systems, backup storage with tens of copies. The latency is 6 months, armies of people are necessary to run it.
You can run a full node on a home computer. No backup is necessary or wanted, the node is the base system and the backup at the same time. Any fool can do it, there is no need for a job contract, all transactions are completely cleared after an hour.
The developers and others have analyzed it. Storage and network is not a problem. There will always be a limit, that is why transactions will cost something for the users.
Why would a CC company convert USD debt into Bitcoins?
It sounds like you're suggesting that the credit card companies would use Bitcoin as a money transfer backbone. Why bother? They might as well manage their own internal ledger and not deal with a public blockchain. Same goes for banks (and of course, this is exactly what they do). Honestly, the only area where I see you having a point is in the insane amount of overhead involved in banking. Competition would improve that, in theory, but there isn't much competition at that echelon of power. One positive side-effect of involving people in the process is the reversibility of transactions. That is a huge feature in banking. One bank burns another and there will be hell to pay. It opens the door to negotiations when people make mistakes. About the only parties who don't like chargebacks are merchants (understandably).
They want to do it, when the merchants only want bitcoins, no USD debt money, not before. Probably, the function will be taken over by new companies, not the old.
bitcoin succeeds.