How many people e.g. test -rc kernels compiled with gcc 3.2?
Why would that matter? It either works or not. If it doesn't
work, it can either be fixed, or support for that old compiler
version can be removed.
One bug report "kernel doesn't work / crash / ... when compiled with
gcc 3.2, but works when compiled with gcc 4.2" will most likely be lost
in the big pile of unhandled bugs, not cause the removal of gcc 3.2
support...
The only other policy than "only remove support if things are
badly broken" would be "only support what the GCC team supports",
which would be >= 4.1 now; and there are very good arguments for
supporting more than that with the Linux kernel.
No, it's not about bugs in gcc, it's about kernel+gcc combinations that
are mostly untested but officially supported.
E.g. how many kernel developers use kernels compiled without
unit-at-a-time? And unit-at-a-time does paper over some bugs,
e.g. at about half a dozen section mismatch bugs I've fixed
recently are not present with it.
But as the discussions have shown gcc 4.0 is currently too high for
making a cut, and it is not yet the right time for raising the minimum
required gcc version.