This doesn't even pass the giggle test from a technical perspective - iPad/iPhone is so massively tied to the Mac platform, how could you ever write any sort of meaningful integration with VS2010. You'd have to port all of the UIKit/CoreFoundation libraries over, you'd have to make a Windows version of the iPhone Simulator, you'd have to write a Objective-C compiler from scratch (remember, Microsoft would never ship GCC), that was compatible with GCC, the list goes on and on.
Now, maybe he's announcing a compatible version of Silverlight, or a way to compile SL applications to iPhone/iPad, which makes far more sense, and would be very compelling for developers. From one codebase, you could have a rich website, a desktop app, a WinPhone7 app, and an iPhone/iPad app, and you could write that app in C#, VB, Python or Ruby. That'd be awesome.
That was before GCC switched to GPLv3. However, the point is moot as someone else mentioned Clang, which I could see MS shipping. I did forget about SFU though, good point.
I completely degree with your assessment of the facts.
The debugger is GDB. This is not hard to integrate with on windows, as it already is integrated with on windows.
The compiler is gcc. Objective-C for gcc already exists on windows. Additionally, several people (Appcelerator, Adobe, Corona, Unity3d) have written machine code compliant compilers, I think Microsoft could likely produce one in a small number of weeks if they were being illogical about gcc.
Additionally, Microsoft has pretty much continually shipped gcc for the last 15 years or so depending on the products they were selling in the windows/unix integration sphere (and OS2 tools as well).
You don't need to port all the UIKit/CoreFoundation libraries over, just the simulated versions, which already run on x86. I'm pretty sure that could be done in a reasonable timespan, probably 3-4 months at the most. The rest are cross compiled for the device, and cross compiling is largely the same no matter what your host platform is.
There is 0 chance Silverlight is in any way involved as an implementation platform for general purpose use (but the iPhone simulator may have been ported using it). The entire point of the 3.1.1 language was to tie everyone to C, C++ and Objective-C.
Microsoft already ships cross-compilers (for ARM, for example) with VS. And Microsoft already ships dev tools for mobile platforms with VS (including mobile device emulators, etc.). Moreover, MonoTouch showed that this sort of thing (developing iPhone apps in C#, for example) is eminently possible.
From a technical perspective there are no serious roadblocks.
Now, whether or not this is actual news and not completely unsubstantiated rumor is an entirely different question.
You are uninformed about how the iPhone Simulator works. It is not, in fact, an emulator. It's simply a bunch of iPhone OS programs (SpringBoard, Safari, etc.) compiled against OSX and put in an iPhone-shaped screen. Your iPhone app is actually a userland Mac app compiled for x86.
So here's the problem: no amount of glue (short of shipping all of Snow Leopard for Windows) is going to get you an iPhone Simulator on the windows platform. It depends on OSX so deeply that you get weird behavior because of it (iPhone's accelerometer APIs are tied to your disk's accelerometer on the simulator, which is in the wrong orientation. Only your mac's built-in keyboard, not a USB keyboard, works in the simulator, because the iPhone uses really low-level keyboard APIs in OSX. etc.)
But they can't ship an emulator (or they would already have done so for OSX). Because except on very high-end systems, you're not going to emulate a 600-700mhz ARM plus their graphics chip. And obviously Silverlight & Co are firmly in the game development camp, where performance testing matters.
Now, maybe he's announcing a compatible version of Silverlight, or a way to compile SL applications to iPhone/iPad, which makes far more sense, and would be very compelling for developers. From one codebase, you could have a rich website, a desktop app, a WinPhone7 app, and an iPhone/iPad app, and you could write that app in C#, VB, Python or Ruby. That'd be awesome.