Windows Programming in C++

Yes, learn Win32, even if don't ever intend to write or maintain C/C++ apps.

No, don't bother learning MFC/wxWidget now. MFC does come with its source code, so you can study how some classes implement wrappers for Win32, but that is more interesting to C++ programmers. MFC is has decreased in popularity, though Visual Studio continues to support this older tech. Learn MFC/wxWidget only for an as-needed basis, if you need to maintain some older code.

With C#/Java, you can solve a lot of problems, but there are times when you will need to use Win32 directly to achieve some task. for a variety of reasons. Maybe some functionality is simply missing from .NET/Java, or has a bug that can be avoided by going directly to Win32. Maybe your particular problem to solve has unusual or strict requirements, and you would consider writing a portion of your app in native code using some Win32 calls as necessary. Lots of examples/situations really.

Another reason to learn Win32 is that both .NET/Java are higher level abstractions (which is in itself a good thing), but it really does help to understand the internals for these reasons:

1. You get an appreciation of how much work .NET/Java do for you. Of course, you can do the same things in C/C++, but it takes a lot more work. Consider these two compelling .NET technologies, WPF and WCF, which do a lot work for you.
2. You will better understand resource management. Specifically, both .NET/Java are garbage collected environments, but you must deterministically release OS resources (explicitly calling Dispose), for such things as network connections, window handles, kernel objects, and plenty more. You should never rely on the garbage collector to release these objects for you, since the GC is non-deterministic.
3. Debugging, knowing the internals seriously helps here.
4. Knowing Win32 can sometimes help explain the API design in .NET at least. Some parts of the .NET API are modeled on Win32 API, but some parts of the .NET API are extreme improvements over some truly heinous Win32 API designs (consider the API for using GDI for example).
5. Finally, knowing Win32 can help solve performance problems in your apps.

Win32 won't become antiquated, until the Microsoft's popular operating systems are based on something else. At one point, Microsoft was going to replace Win32/64 with .NET in Vista, but this didn't pan out. Even for whatever replaces Win32/64 is the future, you still need to understand the OS SDK. At the risk of sounding like a salesman, I will say that learning Win32 will in fact help you write more robust applications and will greatly aid your debugging skills, two important items to help you stay employed. I would never hire a windows programmer who doesn't have at least some experience with Win32.

I would suggest "Windows via C/C++" by Richter/Nasarre, as one example of a good book on Win32 (yes, it's obviously geared towards C/C++, but these authors do an excellent job explaining Win32).

Hope this helps.