If Apple's current attitude towards regulators in the EU and individual EU countries is any indication, Apple is pretty unlikely to enter one of the most highly regulated sectors worldwide, banking and financial services. The amount of secrecy and information paranoia baked into Apple's DNA also will make an in-house bank, credit bureau, stock brokerage, money transfer service, or retail lender extremely difficult to operate anywhere other than frontier or possibly emerging markets.
So, my guess is that Apple is working to decrease its reliance on outside providers for some support tasks, such as reporting data to credit bureaus or loss prevention, but we shouldn't hold our breath for an entirely Apple owned and operated

Bank or

Trades.
----------
ETA: Goldman Sachs may not add much to

Card from a customer service perspective but it does bring two
very important things to the the table from Apple's point of view: a fully chartered bank and access to massive amounts of capital. Apple's balance sheet, and consequently its stock price, would look very different if Apple internally funded and operated the

Card. This is due to both regulatory requirements and to the huge number of

Card credit lines. In addition, Apple may have had a lot of leverage with GS because Marcus, GS's retail bank, was launching right around the same time as

Card. GS, in order to jump start Marcus–and to potentially help its investment bank get Apple business–may have given Apple very favorable terms.