tbh i think windows 7 should've been the last serious 32 bit release - it would help force people to move away from their P4s. as for linux, there hasn't really been a compelling reason to use 32 bit unless you are a p4 (or older) user. the only difference is linux is still pretty good with that older hardware, so ditching support for it would be annoying for such users. however, those users seem to be left in the dust in many ways anyway, mainly due to GPU support associated by the P4's (and older) generation.
... [the] Linux kernel is still supporting hardware like the Motorola 68000 (m68k), IBM S390, SPARC, and other older CPU architectures ...
Hey, IBM just released a new S390 processor in 2010, the z196. Technically these processors support z/Architecture 3, which supports 64-bit mode, 32-bit data/31-bit addressing from the namesake S/390, and 32-bit data/24-bit addressing from the S/360. For linux purposes, s390 is used for 31-bit kernels vs. s390x for 64-bit kernels. Oracle is still building SPARC machines as well. Hell, I think you can even buy new 68k chips (microcontrollers, usually). Just because it is older, doesn't mean it isn't in use (also, SPARC is newer than x86...).
tbh i think windows 7 should've been the last serious 32 bit release
Personally, I was surprised that Windows 7 supported 32 bit processors at all, considering the system requirements for Vista. They improved things quite a bit from Vista, but I still think 7 should have been 64-bit only. Windows 8, definitely should have been 64-bit only (on x86). I'm guessing they left the support in for 32-bit tablets.