I hear you on the platform-neutral tools approach, D_G.
All 3 platforms (Apple, Google and Microsoft) support C++ development, and if you have code that does more than frob the GUI, time spent developing and debugging that code in another IDE can be amortized by its portability. Last year I developed a private app this way: developed the core code in Visual Studio, and the wrapped it in the Objective C that is mandatory to provide the GUI on an Apple device.
There are a few other lessons I learned from this outage:
Renew your certificates at half their lifetime, rather than waiting for them to near expiration. Some of the representatives of contract houses that spoke here are probably doing this more to handle their stable of developers than to reduce the impact of extended outages, but it serves well for both applications.
Renew your developer's subscription at the first reminder. Apple reminded me a month before it was ended, and that is probably enough time.
Make sure that you have a number of devices provisioned at all times for development. They don't all have to be yours, but they all have to have cloud-backed and restorable. You don't want to get into the situation where you need to provision a device when the portal is unavailable.
Remember that Apple owes you nothing. You have entered into a binding contract with Apple that allows them to refuse you the privilege of having your app sell in their store, and even to force you to engage a third party to audit your machine, on Apple's behalf. You have consented to binding arbitration in the event of any disagreement. When your role and Apple's role are examined, you see that the burden of obligation is primarily on you, the developer.
When major shakeups occur, try to remain emotionally centered. The chaos that Apple experiences during a shakeup will spill over into your life, and you have to manage your response to be happy and useful. Apple's behavior to this "hacking incident" has demonstrates a classic Level I response in the Capability Maturity Model. This isn't to say that Apple always has this level of performance on the CMM, but it looks like this is how it is with the developers suite.
There are a few other recommendations that are not as pertinent to this outage, but generally apply:
If you are a grazer in the Apple ecosystem, don't use your personal hardware for professional development. Personal equipment walks around, gets pounded, gets broken, gets stolen, gets wet; and becomes unavailable.
Professional development requires dedicated hardware, and requires both software and hardware backup. If your big old Mac Pro 2.66 and its herd of hard drives goes down, you need to have backup hardware right now. You and your clients can't wait for somebody to source you an old graphics card whenever it becomes available.