LP64, LLP64 and the IL32 transition
Instead of looking at this as int being "left behind", I would say you should look at it in terms of not being able to leave behind any size type that might be needed. I suppose compilers could define int32_t in terms of some internal __int32_t extension type, but with C99 still not being widely supported, it would have been a major pain for apps to have to work around missing int32_t definitions when their build systems couldn't find a 32-bit type among the standard types. And having a 32-bit type is essential, regardless of what your native word size is (for instance it's the only correct type for Unicode codepoint values).
For the same reason, it would not be feasible to have made short 32-bit and int 64-bit: a 16-bit type is essential for many things, audio processing being the first that comes to mind. (Not to mention Windows'/Java's ugly UTF-16 obsession..)
Really, I don't think the 16-to-32-bit and 32-to-64-bit transitions are at all comparable. Leaving behind 16-bit was leaving behind a system where most numbers encountered in ordinary, every-day life would not fit in a basic type and where hacks like "far" pointers had to be used to work with nontrivial data sets. On the other hand, most applications have minimal need for 64-bit types. Large monetary figures, multimedia file sizes/offsets, disk positions, high-end databases, memory-mapped access to large files, etc. are some specialized applications that come to mind, but there's no reason to think that a word processor would ever need billions of characters or that a web page would ever need billions of html elements. There are simply fundamental differences in the relationship of the numeric magnitudes to the realities of the physical world, the human mind, etc.
How I see it is that Windows is an oddball in the whole x64 transition. But putting that aside, C or C++ never defined the integral types to be fixed-length. I find the whole int/long/pointer thing quite understandable, if you look at it this way:
int: mostly 32 bits long (Linux, Mac and Windows)long: 64 bits on Mac and Linux, 32 on Windowslong long: 64-bit on Mac, Linux, and Windows x64- (
u)intptr_t: exact length of pointer (32 on 32-bit, 64 on 64-bit systems)
WORD and DWORD are ugly, and should be avoided. If the API forces you to use them, replace DWORD with DWORD_PTR when you're dealing with... well, pointers. It was never correct to use (D)WORD there in the first place IMHO.
I don't think Windows will change its decision, ever. Too much trouble already.
Why was int left behind? Why does Venus rotate in the opposite direction? The answer to the first question is found here (I believe), the second is a bit more complicated ;)